Every one according to the purpose of his heart. As he had enjoined it upon them to give liberally, this, also, required to be added -- that liberality is estimated by God, not so much from the sum, as from the disposition. He was desirous, it is true, to induce them to give largely, in order that the brethren might be the more abundantly aided; but he had no wish to extort any thing from them against their will. Hence he exhorts them to give willingly, whatever they might be prepared to give. He places purpose of heart in contrast with regret and constraint. For what we do, when compelled by necessity, is not done by us with purpose of heart, but with reluctance. [1] Now the necessity meant you must understand to be what is extrinsic, as it is called -- that is, what springs from the influence of others. For we obey God, because it is necessary, and yet we do it willingly. We ourselves, accordingly, in that case impose a necessity of our own accord, and because the flesh is reluctant, we often even constrain ourselves to perform a duty that is necessary for us. But, when we are constrained from the influence of others, having in the mean time an inclination to avoid it, if by any means we could, we do nothing in that case with alacrity -- nothing with cheerfulness, but every thing with reluctance or constraint of mind. For God loveth a cheerful giver He calls us back to God, as I said in the outset, for alms are a sacrifice. Now no sacrifice is pleasing to God, if it is not voluntary. For when he teaches us, that God loveth a cheerful giver, he intimates that, on the other hand, the niggardly and reluctant are loathed by Him. For He does not wish to lord it over us, in the manner of a tyrant, but, as He acts towards us as a Father, so he requires from us the cheerful obedience of children. [2]

Footnotes

1 - "Auec regret et tristesse;" -- "With regret and sadness."

2 - "Vne obeissance filiale, qui soit prompte et franche;" -- "A filial obedience, which is prompt and cheerful."

Every man according as he purposeth in his heart - The main idea in this verse is, that the act of giving should be voluntary and cheerful. It should not seem to be extorted by the importunity of others 2-Corinthians 9:6; nor should it be given from urgent necessity, but it should be given as an offering of the heart. On this part of the verse we may remark:
(1) That the heart is usually more concerned in the business of giving than the head. If liberality is evinced, it will be the heart which prompts to it; if it is not evinced, it will be because the heart has some bad passions to gratify, and is under the influence of avarice, or selfishness, or some other improper attachment. Very often a man is convinced he ought to give liberally, but a narrow heart and a parsimonious spirit prevents it.
(2) we should follow the dictates of the heart in giving. I mean that a man will usually give more correctly who follows the first promptings of his heart when an object of charity is presented, than he will if he takes much time to deliberate. The instinctive prompting of a benevolent heart is to give liberally. And the amount which should be given will usually be suggested to a man by the better feelings of his heart. But if he resolves to deliberate much, and if he suffers the heart to grow cold, and if he defers it, the pleadings of avarice will como in, or some object of attachment or plan of life will rise to view, or he will begin to compare himself with others. and he will give much less than he would have done if he had followed the first impulse of feeling. God implanted the benevolent feelings in the bosom that they should prompt us to do good; and he who acts most in accordance with them is most likely to do what he ought to do; and in general it is the safest and best rule for a man to give just what his heart prompts him to give when an object of charity is presented. Man at best is too selfish to be likely to give too much or to go beyond his means; and if in a few instances it should be done, more would be gained in value in the cultivation of benevolent feeling than would be lost in money. I know of no better rule on the subject, than to cultivate as much as possible the benevolent feelings, and then to throw open the soul to every proper appeal to our charity, and to give just according to the instinctive prompting of the heart.
(3) giving should be voluntary and cheerful. It should be from the heart. Yet there is much, very much that is not so, and there is, therefore, much benevolence that is spasmodic and spurious; that cannot be depended on, and that will not endure. No dependence can be placed on a man in regard to giving who does not do it from the steady influences of a benevolent heart. But there is much obtained in the cause of benevolence that is produced by a kind of extortion It is given because others give, and the man would be ashamed to give less than they do. Or, it is given because he thinks his rank in life demands it, and he is prompted to do it by pride and vanity. Or, he gives from respect to a pastor or a friend, or because he is warmly importuned to give; or because he is shut up to a kind of necessity to give, and must give or he would lose his character and become an object of scorn and detestation. In all this there is nothing cheerful and voluntary; and there can be nothing in it acceptable to God. Nor can it be depended on permanently. The heart is not in it, and the man will evade the duty as soon as he can, and will soon find excuses for not giving at all.
Not grudgingly - Greek, "Not of grief" (μὴ ἐκ λύπης mē ek lupēs). Not as if be were sorry to part with his money. Not as if he were constrained to do a thing that was extremely painful to him. "Or of necessity." As if he were compelled to do it. Let him do it cheerfully.
For God loveth a cheerful giver - And who does not? Valuable as any gift may be in itself, yet if it is forced and constrained; if it can be procured only after great importunity and persevering effort, who can esteem it as desirable? God desires the heart in every service. No service that is not cheerful and voluntary; none that does not arise from true love to him can be acceptable in his sight. God loves it because it shows a heart like his own - a heart disposed to give cheerfully and do good on the largest scale possible; and because it shows a heart attached from principle to his service and cause. The expression here has all the appearance of a proverb, and expressions similar to this occur often in the Scriptures. In an uninspired writer, also, this idea has been beautifully expanded. "In all thy gifts show a cheerful countenance, and dedicate thy tithes with gladness. Give unto the Most High according as he hath enriched thee: and as thou hast gotten give with a cheerful eye. For the Lord recompenseth, and will give thee seven times as much" - Wisdom of the Son of Sirach 35:9-11. In nothing, therefore, is it more important than to examine the motives by which we give to the objects of benevolence. However liberal may be our benefactions, yet God may see that there is no sincerity, and may hate the spirit with which it is done.

Not grudgingly, or of necessity - The Jews had in the temple two chests for alms; the one was של תובה of what was necessary, i.e. what the law required, the other was של נרבה of the free-will offerings. To escape perdition some would grudgingly give what necessity obliged them; others would give cheerfully, for the love of God, and through pity to the poor. Of the first, nothing is said; they simply did what the law required. Of the second, much is said; God loves them. The benefit of almsgiving is lost to the giver when he does it with a grumbling heart. And, as he does not do the duty in the spirit of the duty, even the performance of the letter of the law is an abomination in the sight of God.
To these two sorts of alms in the temple the apostle most evidently alludes. See Schoettgen.

Every man according as he (c) purposeth in his heart, [so let him give]; not (d) grudgingly, or of (e) necessity: for God loveth a cheerful giver.
(c) Determines and appoints freely with himself.
(d) With a sparing and grudging heart.
(e) Against his will, not wanting to have evil spoken of him.

Every man according as he purposeth in his heart,.... Which is not to be understood of the quantity, or any set sum he has fixed upon in his mind to give; but of the quality or nature of giving; or of the manner in which he is to give:
so let him give; of his own will and free choice, from his very heart; not as directed and forced by others, but according to his own counsel and determination:
not grudgingly; or not of grief; with pain and uneasiness of mind, grieving at parting with what is given, reflecting on the persons that move him to it, or on the objects moved for. The Jews (g) reckon this the lowest degree of all in giving alms; "when a man gives to anyone" "with grief", to which the apostle seems to refer: who adds,
or of necessity; of force, by coaction, being obliged to it by the influence, example, or commands of superiors; or through the powerful motives, or prevailing entreaties of others; for without these, men, according to their abilities, should give of themselves freely and liberally:
for God loveth a cheerful giver; or one that gives , "with a cheerful countenance", as the Jews (h) say; or as elsewhere (i), "with a cheerful heart": their rule is this,
"he that doth the commandment, i.e. alms, let him do it , "with a cheerful heart".''
Who looks pleasantly on the person or persons that move him to it, or on the object to whom he gives; who parts with his money willingly, and takes delight in doing good to others; such givers God loves: not that their cheerful beneficence is the cause of his special peculiar love to them in his own heart, which arises from nothing in man, or done by him; but the meaning is, that God does well to such persons; shows his love to them; he lets them know how kindly he takes such acts of theirs, by prospering and succeeding them in their worldly affairs. In the Septuagint in Proverbs 22:8 are these words, "God blesses a cheerful man, and a giver", which the apostle refers to.
(g) Maimon. Mattanot Anayim, c. 10. sect. 14. (h) Maimon. Mattanot Anayim, c. 10. sect. 13. (i) Vajikra Rabba, fol. 174. 1. Parash. 34.

according as he purposeth in his heart--Let the full consent of the free will go with the gift [ALFORD]. Opposed to "of necessity," as "grudgingly" is opposed to "a cheerful giver" (Proverbs 22:9; Proverbs 11:25; Isaiah 32:8).

Of necessity - Because he cannot tell how to refuse.