Sing joyfully to God our strength. This psalm, it is probable, was appointed to be sung on the festival days on which the Jews kept their solemn assemblies. In the exordium, there is set forth the order of worship which God had enjoined. They were not to stand deaf and dumb at the tabernacle; for the service of God does not consist in indolence, nor in cold and empty ceremonies; but they were, by such exercises as are here prescribed, to cherish among themselves the unity of faith; to make an open profession of their piety; to stir up themselves to continual progress therein; to endeavor to join, with one accord, in praising God; and, in short, to continue steadfast in the sacred covenant by which God had adopted them to himself. Such having been the use of festival days under the law, we may conclude, that whenever true believers assemble together at the present day, the end which they ought to have in view is to employ themselves in the exercises of religion -- to call to their remembrance the benefits which they have received from God -- to make progress in the knowledge of his word -- and to testify the oneness of their faith. Men only mock God by presenting to him vain and unprofitable ceremonies, unless the doctrine of faith go before, stirring them up to call upon God; and unless, also, the remembrance of his benefits furnish matter of praise. Yea, rather it is a profanation of his name, when people quench the light of divine truth, and satisfy themselves with performing mere outward service. Accordingly, the faithful are here not only enjoined to come together to the tabernacle, but are also taught the end for which they are to assemble there, which is, that the free and gracious covenant which God has made with them may be brought anew to their remembrance, for increasing their faith and piety, that thus the benefits which they have received from him may be celebrated, and their hearts thereby moved to thanksgiving. With respect to the tabret, harp, and psaltery, we have formerly observed, and will find it necessary afterwards to repeat the same remark, that the Levites, under the law, were justified in making use of instrumental music in the worship of God; it having been his will to train his people, while they were as yet tender and like children, by such rudiments, until the coming of Christ. But now when the clear light of the gospel has dissipated the shadows of the law, and taught us that God is to be served in a simpler form, it would be to act a foolish and mistaken part to imitate that which the prophet enjoined only upon those of his own time. From this, it is apparent that the Papists have shown themselves to be very apes in transferring this to themselves. Under the new moon, by the figure synecdoche, is comprehended all the other high feasts. Sacrifices were daily offered; but the days on which the faithful met together at the tabernacle, according to the express appointment of the law, are called, by way of eminence, the days of sacrifice.

Sing aloud unto God our strength - The strength and support of the nation; he from whom the nation has derived all its power. The word rendered sing aloud means to rejoice; and then, to make or cause to rejoice. It would be appropriate to a high festal occasion, where music constituted an important part of the public service. And it would be a proper word to employ in reference to any of the great feasts of the Hebrews.
Make a joyful noise - A noise indicating joy, as distinguished from a noise of mourning or lamentation.
Unto the God of Jacob - Not here particularly the God of the patriarch himself, but of the people who bore his name - his descendants.

Sing aloud unto God our strength - There is much meaning here: as God is our strength, let that strength be devoted to his service; therefore, sing aloud! This is principally addressed to the priests and Levites.

"To the chief Musician upon (a) Gittith, [A Psalm] of Asaph." Sing (b) aloud unto God our strength: make a joyful noise unto the God of Jacob.
(a) An instrument of music brought from Geth.
(b) It seems that this psalm was appointed for solemn feasts and assemblies of the people to whom for a time these ceremonies were ordained, but now under the gospel are abolished.

Sing aloud unto God our strength,.... The strength of Israel, who, by strength of hand, and a mighty arm, brought Israel out of Egypt, protected and upheld them in the wilderness, and brought them to, and settled and established them in the land of Canaan; and who is the strength of every true Israelite, from whom they have both their natural and spiritual strength; so that they can exercise grace, perform duty, bear afflictions, withstand temptations, fight with and conquer enemies, and hold on and out unto the end; and therefore have reason to sing the praises of God with great fervour, zeal, and affection:
make a joyful noise unto the God of Jacob; or Israel, being the God that had made a covenant with them, had chosen them for his peculiar people, and had redeemed them out of the house of bondage, and bestowed peculiar favours upon them; and therefore were under obligation to show forth his praise vocally and audibly, and with strong expressions of joy; and the spiritual Israel of God much more so, who have an interest in the covenant of grace, and share in electing, redeeming, and calling grace, by all which he appears to be their God and Father, in a special sense.

All the worship we can render to the Lord is beneath his excellences, and our obligations to him, especially in our redemption from sin and wrath. What God had done on Israel's behalf, was kept in remembrance by public solemnities. To make a deliverance appear more gracious, more glorious, it is good to observe all that makes the trouble we are delivered from appear more grievous. We ought never to forget the base and ruinous drudgery to which Satan, our oppressor, brought us. But when, in distress of conscience, we are led to cry for deliverance, the Lord answers our prayers, and sets us at liberty. Convictions of sin, and trials by affliction, prove his regard to his people. If the Jews, on their solemn feast-days, were thus to call to mind their redemption out of Egypt, much more ought we, on the Christian sabbath, to call to mind a more glorious redemption, wrought out for us by our Lord Jesus Christ, from worse bondage.

Gittith--(See on Psalm 8:1, title). A festal Psalm, probably for the passover (compare Matthew 26:30), in which, after an exhortation to praise God, He is introduced, reminding Israel of their obligations, chiding their neglect, and depicting the happy results of obedience. (Psalm. 81:1-16)
our strength-- (Psalm 38:7).

The summons in Psalm 81:2 is addressed to the whole congregation, inasmuch as הריעוּ is not intended of the clanging of the trumpets, but as in Ezra 3:11, and frequently. The summons in Psalm 81:3 is addressed to the Levites, the appointed singers and musicians in connection with the divine services, 2-Chronicles 5:12, and frequently. The summons in Psalm 81:4 is addressed to the priests, to whom was committed not only the blowing of the two (later on a hundred and twenty, vid., 2-Chronicles 5:12) silver trumpets, but who appear also in Joshua 6:4 and elsewhere (cf. Psalm 47:6 with 2-Chronicles 20:28) as the blowers of the shophar. The Talmud observes that since the destruction of the Temple the names of instruments שׁופרא and חצוצרתּא are wont to be confounded one for the other (B. Sabbath 36a, Succa 34a), and, itself confounding them, infers from Numbers 10:10 the duty and significance of the blowing of the shophar (B. Erachin 3b). The lxx also renders both by σάλπιγξ; but the Biblical language mentions שׁופר and חצצרה, a horn (more especially a ram's horn) and a (metal) trumpet, side by side in Psalm 98:6; 1-Chronicles 15:28, and is therefore conscious of a difference between them. The Tפra says nothing of the employment of the shophar in connection with divine service, except that the commencement of every fiftieth year, which on this very account is called שׁנת היּבל, annus buccinae, is to be made known by the horn signal throughout all the land (Leviticus 25:9). But just as tradition by means of an inference from analogy derives the blowing of the shophar on the first of Tishri, the beginning of the common year, from this precept, so on the ground of the passage of the Psalm before us, assuming that בּחרשׁ, lxx ἐν νεομηνίᾳ, refers not to the first of Tishri but to the first of Nisan, we may suppose that the beginning of every month, but, in particular, the beginning of the month which was at the same time the beginning of the ecclesiastical year, was celebrated by a blowing of the shophar, as, according to Josephus, Bell. iv. 9, 12, the beginning and close of the Sabbath was announced from the top of the Temple by a priest with the salpinx. The poet means to say that the Feast of the Passover is to be saluted by the congregation with shouts of joy, by the Levites with music, and even beginning from the new moon (neomenia) of the Passover month with blowing of shophars, and that this is to be continued at the Feast of the Passover itself. The Feast of the Passover, for which Hupfeld devises a gloomy physiognomy,
(Note: In the first of his Commentationes de primitiva et vera festorum apud Hebraeos ratione, 1851, 4to.)
was a joyous festival, the Old Testament Christmas. 2-Chronicles 30:21 testifies to the exultation of the people and the boisterous music of the Levite priests, with which it was celebrated. According to Numbers 10:10, the trumpeting of the priests was connected with the sacrifices; and that the slaying of the paschal lambs took place amidst the Tantaratan of the priests (long-drawn notes interspersed with sharp shrill ones, תקיעה תרועה וקיעה), is expressly related of the post-exilic service at least.
(Note: Vid., my essay on the Passover rites during the time of the second Temple in the Luther. Zeitschr. 1855; and cf. Armknecht, Die heilige Psalmidoe (1855), S. 5.)
The phrase נתן תּף proceeds from the phrase נתן קול, according to which נתן directly means: to attune, strike up, cause to be heard. Concerning כּסה (Proverbs 7:20 כּסא) tradition is uncertain. The Talmudic interpretation (B. Rosh ha-Shana 8b, Betza 16a, and the Targum which is taken from it), according to which it is the day of the new moon (the first of the month), on which the moon hides itself, i.e., is not to be seen at all in the morning, and in the evening only for a short time immediately after sunset, and the interpretation that is adopted by a still more imposing array of authorities (lxx, Vulgate, Menahem, Rashi, Jacob Tam, Aben-Ezra, Parchon, and others), according to which a time fixed by computation (from כּסה = כּסס, computare) is so named in general, are outweighed by the usage of the Syriac, in which Keso denotes the full moon as the moon with covered, i.e., filled-up orb, and therefore the fifteenth of the month, but also the time from that point onwards, perhaps because then the moon covers itself, inasmuch as its shining surface appears each day less large (cf. the Peshto, 1-Kings 12:32 of the fifteenth day of the eighth month, 2-Chronicles 7:10 of the twenty-third day of the seventh month, in both instances of the Feast of Tabernacles), after which, too, in the passage before us it is rendered wa-b-kese, which a Syro-Arabic glossary (in Rosenmller) explains festa quae sunt in medio mensis. The Peshto here, like the Targum, proceeds from the reading חגּינוּ, which, following the lxx and the best texts, is to be rejected in comparison with the singular חגּנוּ. If, however, it is to be read chgnw, and כּסה (according to Kimchi with Segol not merely in the second syllable, but with double Segol כּסה, after the form טנא = טנא) signifies not interlunium, but plenilunium (instead of which also Jerome has in medio mense, and in Proverbs 7:20, in die plenae lunae, Aquila ἡμέρᾳ πανσελήνου), then what is meant is either the Feast of Tabernacles, which is called absolutely החג in 1-Kings 8:2 (2-Chronicles 5:3) and elsewhere, or the Passover, which is also so called in Isaiah 30:29 and elsewhere. Here, as Psalm 81:5 will convince us, the latter is intended, the Feast of unleavened bread, the porch of which, so to speak, is ערב פּסח together with the ליל שׁמּרים (Exodus 12:42), the night from the fourteenth to the fifteenth of Nisan. In Psalm 81:2, Psalm 81:3 they are called upon to give a welcome to this feast. The blowing of the shophar is to announce the commencement of the Passover month, and at the commencement of the Passover day which opens the Feast of unleavened bread it is to be renewed. The ל of ליום is not meant temporally, as perhaps in Job 21:30 : at the day = on the day; for why was it not ביום? It is rather: towards the day, but בכסה assumes that the day has already arrived; it is the same Lamed as in Psalm 81:2, the blowing of the shophar is to concern this feast-day, it is to sound in honour of it.