But to do good, etc. Here he points out even another way of offering a due and regular sacrifice, for all the acts and duties of love are so many sacrifices; and he thereby intimates that they were foolish and absurd in their wishes who thought that something was wanting except they offered beasts to God according to the Law, since God gave them many and abundant opportunities for sacrificing. For though he can derive no benefit from us, yet he regards prayer a sacrifice, and so much as the chief sacrifice, that it alone can supply the place of all the rest; and then, whatever benefits we confer on men he considers as done to himself, and honors them with the name of sacrifices. So it appears that the elements of the Law are now not only superfluous, but do harm, as they draw us away from the right way of sacrificing. The meaning is, that if we wish to sacrifice to God, we must call on him and acknowledge his goodness by thanksgiving, and further, that we must do good to our brethren; these are the true sacrifices which Christians ought to offer; and as to other sacrifices, there is neither time nor place for them. For with such sacrifices God is well pleased. There is to be understood here an implied contrast, -- that he no longer requires those ancient sacrifices which he had enjoined until the abrogation of the Law. But with this doctrine is connected an exhortation which ought powerfully to stimulate us to exercise kindness towards our neighbors; for it is not a common honor that God should regard the benefits we confer on men as sacrifices offered to himself, and that he so adorns our works, which are nothing worth, as to pronounce them holy and sacred things, acceptable to him. When, therefore, love does not prevail among us, we not only rob men of their right, but God himself, who has by a solemn sentence dedicated to himself what he has commanded to be done to men. The word communicate has a wider meaning than to do good, for it embraces all the duties by which men can mutually assist one another; and it is a true mark or proof of love, when they who are united together by the Spirit of God communicate to one another. [1]

Footnotes

1 - The words may be thus rendered, "And forget not benevolence (or, literally, well-doing) and liberality." The de here should be rendered "and," for this is enjoined in addition to what is stated in the previous verse. The word eupoiia means kindness, benevolence, beneficence, the doing of good generally; but koinonia refers to the distribution of what is needful for the poor. See Romans 15:26, 2-Corinthians 9:13. So that Calvin in this instance has reserved their specific meaning. Stuart's version is "Forget not kindness also and liberality;" and he explains the clause thus, "Beneficence or kindness toward the suffering and liberality toward the needy." -- Ed

But to do good, and to communicate, forget not - To communicate or impart to others; that is, to share with them what we have. The Greek word means having in common with others. The meaning is, that they were to show liberality to those who were in want, and were to take special pains not to forget this duty. We are prone to think constantly of our own interests, and there is great danger of forgetting the duty which we owe to the poor and the needy. On the duty here enjoined, see the notes on Galatians 6:10.
For with such sacrifices God is well pleased - He is pleased with the sacrifices of prayer and of praise; with the offerings of a broken and a contrite heart: but he is especially pleased with the religion which leads us to do good to others. This was eminently the religion of his Son, the Lord Jesus; and to this all true religion prompts. The word "sacrifices" here is not taken in a strict sense, as denoting what is offered as an expiation for sin, or in the sense that we are by doing good to attempt to make atonement for our transgressions, but in the general sense of an offering made to God. God is pleased with this:
(1) because it shows in us a right state of heart;
(2) because it accords with his own nature. He does good continually, and he is pleased with all who evince the same spirit.

But to do good and to communicate - These are continual sacrifices which God requires, and which will spring from a sense of God's love in Christ Jesus. Praise to God for his unspeakable gift, and acts of kindness to men for God's sake. No reliance, even on the infinitely meritorious sacrifice of Christ, can be acceptable in the sight of God if a man have not love and charity towards his neighbor. Praise, prayer, and thanksgiving to God, with works of charity and mercy to man, are the sacrifices which every genuine follower of Christ must offer: and they are the proofs that a man belongs to Christ; and he who does not bear these fruits gives full evidence, whatever his creed may be, that he is no Christian.

But to do good and to communicate forget not,.... Which is to be understood, not of doing good works in general, but of acts of beneficence, or communicating to "the poor", as the Syriac version renders it: the apostle proceeds to take notice of another sort of sacrifice, which continues under the Gospel dispensation; and that is, alms; which should be attended to: alms should be given, or beneficence be exercised to all men in need, even to our enemies, as well as to our friends and relations; and especially to poor saints, and ministers of the Gospel: and this believers should not "forget"; which shows that it is a duty of importance; and that men are too apt to neglect it, and should be stirred up unto it:
for with such sacrifices God is well pleased; not that they are meritorious of the favour of God and of eternal life; for what a man gives in a way of charity is but what God has given him, and cannot be profitable to God, though it is to a fellow creature; nor is there any proportion between what is given, and grace and glory which the saints receive; yet doing good in this way, when it is done in faith, springs from love, and is directed to the glory of God, is well pleasing to him; yea, these sacrifices are preferred by him to legal ones, Hosea 6:6 and the Jews also say, that
"greater is he who does alms than (if he offered) all sacrifices (c).''
(c) T. Bab. Succa, fol. 49. 2.

We must, according to our power, give to the necessities of the souls and bodies of men: God will accept these offerings with pleasure, and will accept and bless the offerers through Christ. The apostle then states what is their duty to living ministers; to obey and submit to them, so far as is agreeable to the mind and will of God, made known in his word. Christians must not think themselves too wise, too good, or too great, to learn. The people must search the Scriptures, and so far as the ministers teach according to that rule, they ought to receive their instructions as the word of God, which works in those that believe. It is the interest of hearers, that the account their ministers give of them may be with joy, and not with grief. Faithful ministers deliver their own souls, but the ruin of a fruitless and faithless people will be upon their own heads. The more earnestly the people pray for their ministers, the more benefit they may expect from their ministry. A good conscience has respect to all God's commands, and all our duty. Those who have this good conscience, yet need the prayers of others. When ministers come to a people who pray for them, they come with greater satisfaction to themselves, and success to the people. We should seek all our mercies by prayer. God is the God of peace, fully reconciled to believers; who has made a way for peace and reconciliation between himself and sinners, and who loves peace on earth, especially in his churches. He is the Author of spiritual peace in the hearts and consciences of his people. How firm a covenant is that which has its foundation in the blood of the Son of God! The perfecting of the saints in every good work, is the great thing desired by them, and for them; and that they may at length be fitted for the employment and happiness of heaven. There is no good thing wrought in us, but it is the work of God. And no good thing is wrought in us by God, but through Christ, for his sake and by his Spirit.

But--But the sacrifice of praise with the lips (Hebrews 13:15) is not enough; there must be also doing good (beneficence) and communicating (that is, imparting a share of your means, Galatians 6:6) to the needy.
with such--and not mere ritualistic sacrifices.

But. Thanksgiving is not all: there must be good deeds.
Communicate. Give of our goods.
Such sacrifices. These givings for God's purposes are sacrifices that please him.
Obey them that have the rule over you. Your elders or bishops.
They watch for your souls. Give them deference on this account, and because they must give account to the Master of those committed to their trust.
Pray for us. Paul often makes this request. He refers to his uprightness of life perhaps because he had been arrested as an evil doer in Jerusalem.
I beseech you the rather for your prayers that I may be the sooner released and returned to you. Paul had been torn away from Jerusalem, and finally sent to Rome as a prisoner. The language here implies the imprisonment of the writer.
The God of peace, who gives us peace.
That great Shepherd. Christ, "the Good Shepherd."
Through the blood of the everlasting covenant. The blood of Christ on the cross sealed the everlasting covenant of the Gospel of which the resurrection of Christ from the dead was the surety.
Make you perfect in every good work. By supplying what is defective.
Working in you. See Philippians 2:13. God works in us by his Spirit.