These verses cast light upon the preceding context. Had it been stated in unqualified terms that sacrifices were of no value, we might have been perplexed to know why in that case they were instituted by God; but the difficulty disappears when we perceive that they are spoken of only in comparison with the true worship of God. From this we infer, that when properly observed, they were far from incurring divine condemnation. There is in all men by nature a strong and ineffaceable conviction that they ought to worship God. Indisposed to worship him in a pure and spiritual manner, it becomes necessary that they should invent some specious appearance as a substitute; and however clearly they may be persuaded of the vanity of such conduct, they persist in it to the last, because they shrink from a total renunciation of the service of God. Men have always, accordingly, been found addicted to ceremonies until they have been brought to the knowledge of that which constitutes true and acceptable religion. Praise and prayer are here to be considered as representing the whole of the worship of God, according to the figure synecdoche. The Psalmist specifies only one part of divine worship, when he enjoins us to acknowledge God as the Author of all our mercies, and to ascribe to him the praise which is justly due unto his name: and adds, that we should betake ourselves to his goodness, cast all our cares into his bosom, and seek by prayer that deliverance which he alone can give, and thanks for which must afterwards be rendered to him. Faith, self-denial, a holy life, and patient endurance of the cross, are all sacrifices which please God. But as prayer is the offspring of faith, and uniformly accompanied with patience and mortification of sin, while praise, where it is genuine, indicates holiness of heart, we need not wonder that these two points of worship should here be employed to represent the whole. Praise and prayer are set in opposition to ceremonies and mere external observances of religion, to teach us, that the worship of God is spiritual. Praise is first mentioned, and this might seem an inversion of natural order. But in reality it may be ranked first without any violation of propriety. An ascription to God of the honor due unto his name lies at the foundation of all prayer, and application to him as the fountain of goodness is the most elementary exercise of faith. Testimonies of his goodness await us ere yet we are born into the world, and we may therefore be said to owe the debt of gratitude before we are called to the necessity of supplication. Could we suppose men to come into the world in the full exercise of reason and judgment, their first act of spiritual sacrifice should be that of thanksgiving. There is no necessity, however, for exercising our ingenuity in defense of the order here adopted by the Psalmist, it being quite sufficient to hold that he here, in a general and popular manner, describes the spiritual worship of God as consisting in praise, prayer, and thanksgiving. In the injunction here given, to pay our vows, there is an allusion to what was in use under the ancient dispensation, "What shall I render unto the Lord for all his benefits towards me? I will take the cup of salvation, and call upon the name of the Lord." - Psalm 116:12, 13 What the words inculcate upon the Lord's people is, in short, gratitude, which they were then in the habit of testifying by solemn sacrifices. But we shall now direct our attention more particularly to the important point of the doctrine which is set before us in this passage. And the first thing deserving our notice is, that the Jews, as well as ourselves, were enjoined to yield a spiritual worship to God. Our Lord, when he taught that this was the only acceptable species of worship, rested his proof upon the one argument, that "God is a spirit," (John 4:24.) He was no less a spirit, however, under the period of the legal ceremonies than after they were abolished; and must, therefore, have demanded then the same mode of worship which he now enjoins. It is true that he subjected the Jews to the ceremonial yoke, but in this he had a respect to the age of the Church; as afterwards, in the abrogation of it, he had an eye to our advantage. In every essential respect the worship was the same. The distinction was one entirely of outward form, God accommodating himself to their weaker and unripe apprehensions by the rudiments of ceremony, while he has extended a simple form of worship to us who have attained a maturer age since the coming of Christ. In himself there is no alteration. The idea entertained by the Manicheans, that the change of dispensation necessarily inferred a change in God himself, was as absurd as it would be to arrive at a similar conclusion from the periodical alterations of the seasons. These outward rites are, therefore, in themselves of no importance, and acquire it only in so far as they are useful in confirming our faith, so that we may call upon the name of the Lord with a pure heart. The Psalmist, therefore, justly denounces the hypocrites who gloried in their ostentatious services, and declares that they observed them in vain. It may occur to some, that as sacrifices sustained a necessary place under the Law, they could not be warrantably neglected by the Jewish worshipper; but by attending to the scope of the Psalmist, we may easily discover that he does not propose to abrogate them so far as they were helps to piety, but to correct that erroneous view of them, which was fraught with the deepest injury to religion. In the fifteenth verse we have first an injunction to prayer, then a promise of its being answered, and afterwards a call to thanksgiving. We are enjoined to pray in the day of trouble, but not with the understanding that we are to pray only then, for prayer is a duty incumbent upon us every day, and every moment of our lives. Be our situation ever so comfortable and exempt from disquietude, we must never cease to engage in the exercise of supplication, remembering that, if God should withdraw his favor for a moment, we would be undone. In affliction, however our faith is more severely tried, and there is a propriety in specifying it as the season of prayer; the prophet pointing us to God as the only resort and means of safety in the day of our urgent necessity. A promise is subjoined to animate us in the duty, disposed as we are to be overwhelmed by a sense of the majesty of God, or of our own unworthiness. Gratitude is next enjoined, in consideration of God's answer to our prayers. Invocation of the name of God being represented in this passage as constituting a principal part of divine worship, all who make pretensions to piety will feel how necessary it is to preserve the pure and uncorrupted form of it. We are forcibly taught the detestable nature of the error upon this point entertained by the Papists, who transfer to angels and to men an honor which belongs exclusively to God. They may pretend to view these in no other light than as patrons, who pray for them to God. But it is evident that these patrons are impiously substituted by them in the room of Christ, whose mediation they reject. It is apparent, besides, from the form of their prayers, that they recognize no distinction between God and the very least of their saints. They ask the same things from Saint Claudius which they ask from the Almighty, and offer the prayer of our Lord to the image of Catherine. I am aware that the Papists justify their invocation of the dead, by denying that their prayers to them amount to divine worship. They talk so much about the kind of worship which they call latria, that is, the worship which they give to God alone, as to make it appear, that in the invocation of angels and saints they give none of it to them. [1] But it is impossible to read the words of the Psalmist, now under our consideration, without perceiving that all true religion is gone unless God alone is called upon. Were the Papists asked whether it were lawful to offer sacrifices to the dead, they would immediately reply in the negative. They grant to this day that sacrifice could not lawfully be offered to Peter or to Paul, for the common sense of mankind would dictate the profanity of such an act. And when we here see God preferring the invocation of his name to all sacrifices, is it not plain to demonstration, that those who call upon the dead are chargeable with the grossest impiety? From this it follows, that the Papists, let them abound as they may in their genuflections before God, rob him of the chief part of his glory when they direct their supplications to the saints. [2] The express mention which is made in these verses of affliction is fitted to comfort the weak and the fearful believer. When God has withdrawn the outward marks of his favor, a doubt is apt to steal into our minds whether he really cares for our salvation. So far is this from being well founded, that adversity is sent to us by God, just to stir us up to seek him and to call upon his name. Nor should we overlook the fact, that our prayers are only acceptable when we offer them in compliance with the commandment of God, and are animated to them by a consideration of the promise which he has extended. The argument which the Papists have drawn from the passage, in support of their multiplied vows, is idle and unwarrantable. The Psalmist, as we have already hinted, when he enjoins the payment of their vows, refers only to solemn thanksgiving, whereas they trust in their vows as meriting salvation. They contract vows, beside, which have no divine warrant, but, on the contrary, are explicitly condemned by the word of God.

Footnotes

1 - The Papists have different words by which they express different degrees of worship. The term latreia, or latria, they say, denotes the divine worship which exclusively belongs to God, and which they yield to him alone; while douleia, or dulia, signifies that inferior sort of worship which is due to angels and departed saints, and which alone they yield to them. They have also a third degree, which they call huperdouleia, or hyperdulia, that superior kind of inferior worship which they yield to the Virgin Mary. These distinctions are had recourse to, merely to evade the charge of idolatry. But if the Papists yield to angels and glorified saints the honor due only to God, it is of little consequence by what name it is called. Besides, the words latreai and douleai are used indifferently by classic Greek authors, by the Greek fathers, by the Septuagint, and in the New Testament, to express divine worship. In the New Testament, douleia frequently denotes divine worship. Thus we read, in 1-Thessalonians 1:9, "Ye turned to God from idols, douleuein to Theo zonti, to serve the living God;" and in Galatians 4:8, it is said of the Galatians in their heathen state, that "edouleusan, they did service unto them which, by nature, are no gods." -- See Calvin's Institutes, Book I. chap.12, sections 2 and 3; Turretine's Works, volume 4, De Necessaria Secessione Nostra ab Ecclesia Romana, pp. 50-53; and M'Gavin's Protestant, volume1, No. 42, p. 334.

2 - The subject of the invocation of departed saints is discussed at length in Calvin's Institutes, Book III. chap. 20, sections 21-27.

Offer unto God thanksgiving - The word rendered "offer" in this place - זבח zâbach - means properly "sacrifice." So it is rendered by the Septuagint, θῦσον thuson - and by the Vulgate, "immola." The word is used, doubtless, with design - to show what was the "kind" of sacrifice with which God would be pleased, and which he would approve. It was not the mere "sacrifice" of animals, as they commonly understood the term; it was not the mere presentation of the bodies and the blood of slain beasts; it was an offering which proceeded from the heart, and which was expressive of gratitude and praise. This is not to be understood as implying that God did not require or approve of the offering of bloody sacrifices, but as implying that a higher sacrifice was necessary; that these would be vain and worthless unless they were accompanied with the offerings of the heart; and that his worship, even amidst outward forms, was to be a spiritual worship.
And pay thy vows unto the Most High - To the true God, the most exalted Being in the universe. The word "vows" here - נדר neder - means properly a vow or promise; and then, a thing vowed; a votive offering, a sacrifice. The idea seems to be, that the true notion to be attached to the sacrifices which were prescribed and required was, that they were to be regarded as expressions of internal feelings and purposes; of penitence; of a deep sense of sin; of gratitude and love; and that the design of such sacrifices was not fulfilled unless the "vows" or pious purposes implied in the very nature of sacrifices and offerings were carried out in the life and conduct. They were not, therefore, to come merely with these offerings, and then feel that all the purpose of worship was accomplished. They were to carry out the true design of them by lives corresponding with the idea intended by such sacrifices - lives full of penitence, gratitude, love, obedience, submission, devotion. This only could be acceptable worship. Compare the notes at Isaiah 1:11-17. See also Psalm 76:11; Ecclesiastes 5:5.

Offer unto God thanksgiving; and pay thy vows unto the Most High - זבח zebach, "sacrifice unto God, אלהים Elohim, the תודה todah, thank-offering," which was the same as the sin-offering, viz. a bullock, or a ram, without blemish; only there were, in addition, "unleavened cakes mingled with oil, and unleavened wafers anointed with oil; and cakes of fine flour mingled with oil and fried," Leviticus 7:12.
And pay thy vows - נדריך nedareycha, "thy vow-offering, to the Most High." The neder or vow-offering was a male without blemish, taken from among the beeves, the sheep, or the goats. Compare Leviticus 22:19 with Psalm 50:22. Now these were offerings, in their spiritual and proper meaning, which God required of the people: and as the sacrificial system was established for an especial end - to show the sinfulness of sin, and the purity of Jehovah, and to show how sin could be atoned for, forgiven, and removed; this system was now to end in the thing that it signified, - the grand sacrifice of Christ, which was to make atonement, feed, nourish, and save the souls of believers unto eternal life; to excite their praise and thanksgiving; bind them to God Almighty by the most solemn vows to live to him in the spirit of gratitude and obedience all the days of their life. And, in order that they might be able to hold fast faith and a good conscience, they were to make continual prayer to God, who promised to hear and deliver them, that they might glorify him, Psalm 50:15.
From the Psalm 50:16 to the Psalm 50:22 Asaph appears to refer to the final rejection of the Jews from having any part in the true covenant sacrifice.

Offer unto God thanksgiving; and (l) pay thy vows unto the most High:
(l) Show yourself mindful of God's benefits by thanksgiving.

Offer unto God thanksgiving,.... Which is a sacrifice, Psalm 50:23; and the Jews say (x), that all sacrifices will cease in future time, the times of the Messiah, but the sacrifice of praise; and this should be offered up for all mercies, temporal and spiritual; and unto God, because they all come from him; and because such sacrifices are well pleasing to him, and are no other than our reasonable service, and agreeably to his will; and then are they offered up aright when they are offered up through Christ, the great High Priest, by whom they are acceptable unto God, and upon him the altar, which sanctifies every gift, and by faith in him, without which it is impossible to please God. Some render the word "confession" (y); and in all thanksgivings it is necessary that men should confess their sins and unworthiness, and acknowledge the goodness of God, and ascribe all the glory to him; for to him, and him only, is this sacrifice to be offered: not to man; for that would be to sacrifice to his own net, and burn incense to his drag;
and pay thy vows unto the most High: meaning not ceremonial ones, as the vow of the Nazarite; nor to offer such and such a sacrifice, since these are distinguished from and opposed unto the sacrifices of the ceremonial law before mentioned; and much less monastic ones, as the vow of celibacy, and abstinence from certain meats at certain times; but moral, or spiritual and evangelical ones; such as devoting one's self to the Lord and to his service and worship, under the influence and in the strength of grace; signified by saying, I am the Lord's, and the giving up ourselves to him and to his churches, to walk with them in all his commands and ordinances, to which his love and grace constrain and oblige; see Isaiah 44:5; and particularly by them may be meant giving God the glory and praise of every mercy and deliverance, as was promised previous to it; hence those are put together, Psalm 65:1. This Scripture does not oblige to the making of vows, but to the payment of them when made; see Ecclesiastes 5:4; and may refer to everything a man lays himself in a solemn manner under obligation to perform, especially in religious affairs.
(x) Vajikra Rabba, fol. 153. 1. & 168. 4. (y) "confessionem", Montanus, Cocceius, Gejerus, Michaelis; so Ainsworth.

Offer - If thou wouldest know what sacrifices I prize, and indispensably require, in the first place, it is that of thankfulness, proportionable to my great and numberless favours; which doth not consist barely in verbal acknowledgments, but proceeds from an heart deeply affected with God's mercies, and is accompanied with such a course of life, as is well - pleasing to God. Vows - Those substantial vows and promises, which were the very soul of their sacrifices.