John Chrysostom

How was it that he "believed in hope against hope?" It was against man's hope, in hope which is of God. (For he is showing the loftiness of the action, and leaving no room for disbelieving what is said.) Things which are contrary to one another, yet faith blends them together. But if he were speaking about such as were from Ishmael, this language would be superfluous: for it was not by faith but by nature that they were begotten. But he bringeth Isaac also before us. For it was not concerning those nations that he believed, but concerning him who was to be from his barren wife. If then it be a reward to be father of many nations, it would be so of those nations clearly of whom he so believed. For that you may know that he is speaking of them, listen to what follows.