Matthew Poole and continuators on Romans 9:10

10. And not only this , but when Rebecca also had conceived by one, even by our father Isaac ,

Some read it, and not only she (The Particle This is not in the Greek.)

This Instance is added, because there might be some Objection against the former; as if there were some reason why God chose Isaac, and refused Ishmael. Isaac was Born of a Free-woman, and when Abraham was circumcised; but Ishmael was Born of a Bond-woman, and when Abraham was uncircumcised: Besides, Ishmael no sooner came to Years, but he shewed some Tokens of Perversness, and of a wicked Spirit. Therefore, in this, and the Three following Verses, he doth give another, which was beyond all Exception; and that is in Esau and Iacob, betwixt whom there was no Disparity, either in Birth or in Works: They had both one and the same Mother; Rebecca Conceived with them at one and the same time; and that by no other Person, than our Father Isaac; and yet the one of these is Chosen, and the other Refused. This now was an undeniable Proof, that the promise belongs not to all the Children of Abraham, or of Isaac, according to the Flesh; All the Seed of neither are the Children of the promise.

Marginal references: Gen. 25.21.