Romans 9:10

"And not only this; but when Rebecca also had conceived by one, even by our father Isaac." The subject in question was an important one. Hence he turns to several arguments, and endeavors by all means to solve the difficulty. For if it was at once strange and new for them to be cast out after so great promises, it is much more strange that we even should come into their good things, who did not expect anything of the kind. I might, he implies, have mentioned the children by Keturah besides, but I do not. But to gain the victory from a vantage ground it is those born of one and the same father, and mother too, that I bring forward. For they were both sprung from Rebecca, and from Isaac the true-born, the elect, the son honored above all, of whom He said, "In Isaac shall thy seed be called," who became "the father of us all;" but if he was our father, then should his sons have been our fathers; yet it was not so. You see how this happens not in Abraham's case only, but also in that of his son himself, and how it is faith and virtue in all cases that is conspicuous, and gives the real relationship its character.