Galatians 3:18

For if the inheritance is of the law, it is no more of promise: but God hath granted it to Abraham by promise. [Brethren, I wish to use an illustration taken from our daily business life, viz.: that of our usage concerning contracts or agreements. Now if, when a human contract has once been confirmed, it becomes so sacred that no man will presume to annul or change it without the consent of both parties, much more is a covenant of God's too sacred to be modified or tampered with. But God made such a ratified or confirmed contract or covenant with Abraham, for he spoke promises to Abraham, and to his seed. Not in fact meaning to Abraham and all his posterity, but to Abraham and his spiritual posterity (for he used a word which may be so interpreted), for he did not use the plural "seeds," but the singular "seed," thereby referring especially to Christ as the head of the spiritual posterity. Now, I say therefore, that this covenant, having been confirmed before the law came, still holds good, and can not be annulled by the coming of the law, for the law, as you know, did not come until four hundred and thirty years after the covenant was confirmed. Now, to sum up what I have said, the promise, being given to the seed of Abraham, becomes to them an inheritance, and inheritances do not come from two parties, but from one; so, if the inheritance had been derived from the law, it could not have been derived from the promise also; but it was derived from the promise, since God thus gave it to Abraham. We lack space for the grammatical and chronological difficulties of this passage. Suffice it to say, "seed," being a collective noun, is capable of being applied to many; but it is also, as Paul says, capable of being applied to one, and none of his auditors would object at all to his thus applying it solely to Christ. Again, if the term of four hundred and thirty years is inaccurate, it is the number given in the Septuagint, which was then universally used. And, for argumentative purposes, was sufficiently correct as a round number.]