John Chrysostom

No one could allege, that he had another son, and expected the promise to be fulfilled from him, and therefore confidently offered up this one. "And" (his words are) "he offered up his only-begotten, who had received the promises." Why sayest thou "only-begotten"? What then? Of whom was Ishmael sprung? I mean "only-begotten" (he would say) so far as relates to the word of the promise. Therefore after saying, "Only-begotten," showing that he says it for this reason, he added, "of whom it was said, In Isaac shall thy seed be called," that is, "from" him. Seest thou how he admires what was done by the Patriarch? "In Isaac shall thy seed be called," and that son he brought to be sacrificed.

Afterwards, that no one may suppose he does this in despair, and in consequence of this command had cast away that Faith, but may understand that this also was truly of faith, he says that he retained that faith also, although it seem to be at variance with this. But it was not at variance. For he did not measure the power of God by human reasonings, but committed all to faith.