15 Because the law worketh wrath: for where no law is, there is no transgression.
English Standard Version
15 For the law brings wrath, but where there is no law there is no transgression.
15 A contract drawn up by a hard-nosed lawyer and with plenty of fine print only makes sure that you will never be able to collect. But if there is no contract in the first place, simply a promise - and God's promise at that - you can't break it.
New King James Version
15 because the law brings about wrath; for where there is no law there is no transgression.
New Living Translation
15 For the law always brings punishment on those who try to obey it. (The only way to avoid breaking the law is to have no law to break!)
The promise was made to Abraham long before the law. It points at Christ, and it refers to the promise, Genesis 12:3. In Thee shall all families of the earth be blessed. The law worketh wrath, by showing that every transgressor is exposed to the Divine displeasure. As God intended to give men a title to the promised blessings, so he appointed it to be by faith, that it might be wholly of grace, to make it sure to all who were of the like precious faith with Abraham, whether Jews or Gentiles, in all ages. The justification and salvation of sinners, the taking to himself the Gentiles who had not been a people, were a gracious calling of things which are not, as though they were; and this giving a being to things that were not, proves the almighty power of God. The nature and power of Abraham's faith are shown. He believed God's testimony, and looked for the performance of his promise, firmly hoping when the case seemed hopeless. It is weakness of faith, that makes a man lie poring on the difficulties in the way of a promise. Abraham took it not for a point that would admit of argument or debate. Unbelief is at the bottom of all our staggerings at God's promises. The strength of faith appeared in its victory over fears. God honours faith; and great faith honours God. It was imputed to him for righteousness. Faith is a grace that of all others gives glory to God. Faith clearly is the instrument by which we receive the righteousness of God, the redemption which is by Christ; and that which is the instrument whereby we take or receive it, cannot be the thing itself, nor can it be the gift thereby taken and received. Abraham's faith did not justify him by its own merit or value, but as giving him a part in Christ.