A Commentary by John Stott
The apostle begins the paragraph (verse 15): *To give a human example*. Better, ‘let me give you an everyday illustration’ (JBP). This illustration is taken from the realm of human promises, not a business contract but a will, what we sometimes call a man’s ‘last will and testament’. The Greek word in verses 15 and 17 (*Diatheke*) is translated ‘covenant’ in the Authorized Version because it is used in the Septuagint for the covenants of God. But in the classical Greek and the Papyri it was in common use for a will, and is so translated here by the Revised Standard Version. (Cf. Heb.9:15-17, where the two ideas of a covenant and a will are also linked together.)
The point Paul is making is that the wishes and promises which are expressed in a will are unalterable. It is true that in Roman law, as in English law today, a man could change his will, either by making a new one or by adding codicils. For this reason Paul may be referring to ancient Greek law by which a will, once executed and ratified, could not be revoked or even modified. Or he may be saying that it cannot be altered or annulled by somebody else. It certainly cannot be altered by anybody after the testator has died. Whatever the precise legal background may be, it is an *a fortiori* argument, that if a *man’s* will cannot be set aside or added to, much more are the promises of *God* immutable.
To what divine promise is he alluding? God promised an inheritance to Abraham and his posterity. Paul knew perfectly well that the immediate, literal reference of this promise was to the land of Canaan, which God was going to give to Abraham’s physical descendants. But he also knew that this did not exhaust its meaning; nor was it the ultimate reference in God’s mind. Indeed, it could not have been, for God said that in Abraham’s seed all the families of the earth would be blessed, and how could the whole world be blessed through the Jews living in the land of Canaan? Paul realized that both the ‘land’ which was promised and the ‘seed’ to whom it was promised were ultimately spiritual. God’s purpose was not just to give the land of Canaan to the Jews, but to give salvation (a spiritual inheritance) to believers who are in Christ. Further, Paul argues, this truth was implicit in the word God used, which was not the plural ‘children’ or ‘descendants’, but the singular ‘seed’ or ‘posterity’, a collective noun referring to Christ and to all those who are in Christ by faith (verse 16).
Such was God’s promise. It was free and unconditional. As we might say, there were ‘no strings attached’ There were no works to do, no laws to obey, no merit to establish, no conditions to fulfil. God simply said, ‘I will give you a seed. To your seed I will give the land, and in your seed all the nations of the earth will be blessed.’ His promise was like a will, freely giving the inheritance to a future generation. And like a human will, this divine promise is unalterable. It is still in force today, for it has never been rescinded. God does not make promises in order to break them. He has never annulled or modified his will.
We are now ready to consider verse 17: *This*, Paul continues, *is what I mean: the law, which came four hundred and thirty years afterward, does not annul a covenant previously ratified by God, so as to make the promise void*. If the Judaizers were right, our Christian inheritance (justification) is given to those who keep the law; and if it is ‘by the law, it is no longer by promise’, because you cannot have it both ways. *But God gave it to Abraham by a promise* (verse 18). Notice that He ‘gave’ it. The Greek word *kecharistai* emphasizes both that it is a free gift (a gift of *charis*, ‘grace’) and that it has been given for good (the perfect tense). God has not gone back on His promise. It is as binding as a man’s will; indeed, more so. So every sinner who trusts in Christ crucified for salvation, quite apart from any merit or good works, receives the blessing of eternal life and thus inherits the promise of God made to Abraham.