I speak after the manner of men. By this expression he intended to put them to the blush. It is highly disgraceful and base that the testimony of God should have less weight with us than that of a mortal man. In demanding that the sacred covenant of God shall receive not less deference than is commonly yielded to ordinary human transactions, he does not place God on a level with men. The immense distance between God and men is still left for their consideration. Though it be but a man's covenant. This is an argument from the less to the greater. Human contracts are admitted on all hands to be binding: how much more what God has established? The Greek word diatheke, here used, signifies more frequently, what the Latin versions here render it, (testamentum,) a testament; but sometimes too, a covenant, though in this latter sense the plural number is more generally employed. It is of little importance to the present passage, whether you explain it covenant or testament. The case is different with the Epistle to the Hebrews, where the apostle unquestionably alludes to testaments, (Hebrews 9:16, 17;) but here I prefer to take it simply for the covenant which God made. The analogy from which the apostle argues, would not apply so strictly to a testament as to a covenant. The apostle appears to reason from human bargains to that solemn covenant into which God entered with Abraham. If human bargains be so firm that they can receive no addition, how much more must this covenant remain inviolable?

Brethren, I speak after the manner of men - I draw an illustration from what actually occurs among people. The illustration is, that when a contract or agreement is made by people involving obligations and promises, no one can add to it or take from it. It will remain as it was originally made. So with God. He made a solemn promise to Abraham. That promise pertained to his posterity. The blessing was connected with that promise, and it was of the nature of a compact with Abraham. But if so, then this could not be effected by the Law which was four hundred years after, and the Law must have been given to secure some different object from that designed by the promise made to Abraham, Galatians 3:19. But the promise made to Abraham was designed to secure the "inheritance," or the favor of God; and if so, then the same thing could not be secured by the observance of the Law, since there could not be two ways so unlike each other of obtaining the same thing.
God cannot have two ways of justifying and saving people; and if he revealed a mode to Abraham, and that mode was by faith, then it could not be by the observance of the Law which was given so long after. The main design of the argument and the illustration here (Galatians 3:15 ff) is to show that the promise made to Abraham was by no means made void by the giving of the Law. The Law had another design, which did not interfere with the promise made to Abraham. That stood on its own merits, irrespective of the demands and the design of the Law. It is possible, as Rosenmuller suggests, that Paul may have had his eye on an objection to his view. The objection may have been that there were important acts of legislation which succeeded the promise made to Abraham, and that that promise must have been superseded by the giving of the Law. To this he replies that the Mosaic law given at a late period could not take away or nullify a solemn promise made to Abraham, but that it was intended for a different purpose.
Though it be but a man's covenant - A compact or agreement between man and man. Even in such a case no one can add to it or take from it. The argument here is, that such a covenant or agreement must be much less important than a promise made by God. But even that could not be annulled. How much less, therefore, could a covenant made by God be treated as if it were vain. The word "covenant" here (διαθήκη diathēkē) is in the margin rendered "Testament;" that is, will. So Tyndale renders it. Its proper Classical signification is will or testament, though in the Septuagint and in the New Testament it is the word which is used to denote a covenant or compact; see the note at Acts 3:25. Here it is used in the proper sense of the word covenant, or compact; a mutual agreement between man and man. The idea is, that where such a covenant exists; where the faith of a man is solemnly pledged in this manner, no change can be made in the agreement. It is ratified, and firm, and final. "If it be confirmed." By a seal or otherwise.
No man disannulleth - It must stand. No one can change it. No new conditions can be annexed; nor can there be any drawing back from its terms. It binds the parties to a faithful fulfillment of all the conditions. This is well understood among people; and the apostle says that the same thing must take place in regard to God.

I speak after the manner of men - I am about to produce an example taken from civil transactions. If it be confirmed - If an agreement or bond be signed, sealed, and witnessed, and, in this country, being first duly stamped;
No man disannulleth - It stands under the protection of the civil law, and nothing can be legally erased or added.

(17) Brethren, I speak (i) after the manner of men; Though [it be] but a man's covenant, yet [if it be] (k) confirmed, no man disannulleth, or addeth thereto.
(17) He puts forth two general rules before the next argument, which is the seventh in order. The first is, that it is not lawful to break covenants and contracts which are justly made, and are according to law among men, neither may anything be added to them. The other is, that God did so make a covenant with Abraham, that he would gather together his children who consist both of Jews and Gentiles into one body (as appears by that which has been said before). For he did not say, that he would be the God of Abraham and of his "seeds" (which thing nonetheless should have been said, if he had many and various seeds, such as the Gentiles on the one hand, and the Jews on the other) but that he would be the God of Abraham, and of his "seed", as of one.
(i) I will use an example which is common among you, that you may be ashamed that you do not give as much to God's covenant as you do to man's.
(k) Authenticated, as we say.

Brethren,.... Whereas in Galatians 3:1, he calls them "foolish Galatians", which might seem too harsh and severe, therefore, to mitigate and soften their resentments, he styles them brethren; hoping still well of them, and that they were not so far gone, but that they might be recovered; and imputing the blame and fault rather to their leaders and teachers, than to them:
I speak after the manner of men; agreeably to a Talmudic form of speech in use among the Jews, , "the law speaks according to the language of the children of men", or "after the manner of men" (b), when they argue from any Scripture, in which a word is repeated, and the latter word seems to point out something peculiar: but the apostle's meaning is, that the thing he was about to speak of was taken from among men, in common use with them, and what was obvious to the common sense and understanding of men, and might easily be applied and argued from, as it is by him:
though it be but a man's covenant, or testament, yet if it be confirmed, no man disannulleth or addeth thereto; if a covenant made between men, or a man's will and testament, be confirmed, signed, sealed, and witnessed, in a proper manner, no other man can make them void, or take anything from them, or add anything to them, only the parties concerned by their own will and consent; and if this be the case among men, much less can the covenant of God, confirmed by two immutable things, his word and oath, or his will and testament, or any branch of it, be ever disannulled, or be capable of receiving any addition thereunto. The apostle seems to have a particular respect to that branch of the covenant and will of God, which regards the justification of men in his sight by the righteousness of Christ, to which the false teachers were for adding the works of the law.
(b) T. Bab Ceritot, fol. 11. 1. Bava Metzia, fol. 94. 2. Sanhedrin, fol. 90. 2. Maccot, fol. 12. 1. Vid Halicot Olam, tract 4. c. 3. p. 199.

The covenant God made with Abraham, was not done away by the giving the law to Moses. The covenant was made with Abraham and his Seed. It is still in force; Christ abideth for ever in his person, and his spiritual seed, who are his by faith. By this we learn the difference between the promises of the law and those of the gospel. The promises of the law are made to the person of every man; the promises of the gospel are first made to Christ, then by him to those who are by faith ingrafted into Christ. Rightly to divide the word of truth, a great difference must be put between the promise and the law, as to the inward affections, and the whole practice of life. When the promise is mingled with the law, it is made nothing but the law. Let Christ be always before our eyes, as a sure argument for the defence of faith, against dependence on human righteousness.

I speak after the manner of men--I take an illustration from a merely human transaction of everyday occurrence.
but a man's covenant--whose purpose it is far less important to maintain.
if it be confirmed--when once it hath been ratified.
no man disannulleth--"none setteth aside," not even the author himself, much less any second party. None does so who acts in common equity. Much less would the righteous God do so. The law is here, by personification, regarded as a second person, distinct from, and subsequent to, the promise of God. The promise is everlasting, and more peculiarly belongs to God. The law is regarded as something extraneous, afterwards introduced, exceptional and temporary (Galatians 3:17-19, Galatians 3:21-24).
addeth--None addeth new conditions "making" the covenant "of none effect" (Galatians 3:17). So legal Judaism could make no alteration in the fundamental relation between God and man, already established by the promises to Abraham; it could not add as a new condition the observance of the law, in which case the fulfilment of the promise would be attached to a condition impossible for man to perform. The "covenant" here is one of free grace, a promise afterwards carried into effect in the Gospel.

I speak after the manner of men. I will make a comparison with human affairs.
Though it be but a man's covenant, etc. A covenant, or agreement, among men, after it is ratified, cannot be annulled or altered without the consent of both parties.
Now to Abraham and his seed were the promise made. The covenant with its promises was made with Abraham and his seed. There were promises spoken on several occasion. See Genesis 12:3, Genesis 12:7; Genesis 13:16; Genesis 15:5; Genesis 17:7. The promises of the covenant were to the seed, as well as to Abraham, and hence did not terminate with his death.
He saith not, To seeds, as of many, but . . . to thy seed. This passage has excited much criticism. Many have thought that Paul made a grammatical mistake. Even Luther says: "My dear brother Paul, this argument won't stick." The criticism is that sperma, the Greek word rendered "seed," is a collective noun and may include all Abraham's descendants. Paul elsewhere shows that he knew just the meaning of sperma (Romans 4:18; Romans 9:7), but the question here is not one of grammar, but of spiritual meaning. Paul does not mean that sperma (seed) excludes plurality, but that it implies unity. Not the word "children" or "descendants" is used. This would embrace the children of Ishmael, of Esau, and of Keturah. But there is a seed to whom the promise is given; a seed that embraces many, but is one. That seed is Christ the head, and all in Christ. See 1-Corinthians 12:12. The whole spiritual seed of Abraham concentrates in Christ. The promise is to Christ and all in Christ. Paul understood Greek as well as his critics, and also knew what he meant.
And this I say. He returns to the argument introduced in Galatians 3:15.
That the covenant. He has just shown that this covenant was not only with Abraham, but with his spiritual seed, and hence must continue in effect until Christ came. Hence the law, made over four centuries after the covenant was given, could not disannul it. The covenant made with Abraham is still in force.
Four hundred and thirty years. According to Usher's Chronology, the promise was made to Abraham in B. C. 1921; the law was given at Sinai B. C. 1491; the interval is 430 years. But some have held that Paul made a mistake because in Exodus 12:12 it said that Hebrews were in Egypt 430 years. The matter is easily explained. The Septuagint Version of the Old Testament is the one usually followed by Christ and his apostles. Its translators, following the Hebrew copy before them, render Exodus 12:12, "The sojourning of the children of Israel who dwelt in Egypt, and in the land of Canaan, was four hundred and thirty years." Whether this is right, or our Hebrew text, does not matter. Paul gave the usually received statement. His point was simply that the law was given many ages after the covenant with Abraham.
If the inheritance be of the law. Law and promise exclude each other. The legal heir receives his inheritance by law, if there be no will; one not a legal heir may receive it by the promise of a will. The inheritance was given to Abraham by promise; and ours depends on the promise.

I speak after the manner of men - I illustrate this by a familiar instance, taken from the practice of men. Though it be but a man's covenant, yet, if it be once legally confirmed, none - No, not the covenanter himself, unless something unforeseen occur, which cannot be the case with God. Disannulleth, or addeth thereto - Any new conditions.