Hebrews 11:18

Give me your attention, you who have approached God, who believe yourselves to be faithful. Consider diligently how the faith of the faithful is proved from these words that have been read to us. "After these things," the text says, "God tested Abraham and said to him, 'Abraham, Abraham.' And he said, 'Here I am.' " Observe each detail that has been written. For, if one knows how to dig into the depth, one will find a treasure in the details. Perhaps also the precious jewels of the mysteries lie hidden where they are not esteemed.This man was previously called Abram. Nowhere do we read that God called him by this name or said to him, "Abram, Abram." For God could not call him by a name that was to be abolished, but he calls him by this name which God gave; and not only does God call him by this name, but he also repeats it. And when he had responded, "Here I am," God says to him, "Take your dearest son Isaac, whom you love, and offer him to me. Go," the text says, "into the high land, and there you shall offer him for a holocaust upon one of the mountains which I shall show you." Why God gave him this particular name and called him Abraham, he himself has interpreted. "Because," the text says, "I have made you a father of many nations." God gave him this promise when he had his son Ishmael, but it is promised him that the promise will be fulfilled in a son who will be born of Sarah. He had kindled his soul, therefore, in love for his son not only because of posterity but also in the hope of the promises. But this son, in whom these great and marvelous promises have been made, this son, I say, on whose account his name is called Abraham, "he is ordered to offer for a holocaust to the Lord on one of the mountains." What do you say to these things, Abraham? What kind of thoughts are stirring in your heart? […]

"By faith Abraham, when he was tested, offered up Isaac" as a victim, even though he had received this child with the promise that through him his descendants would have been named. And Abraham never doubted, not even when he was about to kill him, …

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.

Great indeed was the faith of Abraham. For while in the case of Abel, and of Noah, and of Enoch, there was an opposition of reasonings only, and it was necessary to go beyond human reasonings; in this case it was necessary not only to go beyond human reasonings, but to manifest also something more. For what was of God seemed to be opposed to what was of God; and faith opposed faith, and command promise. I mean this: He had said, "Get thee out of thy country, and from thy kindred, and I will give thee this land." "He gave him none inheritance in it, no not so much as to set his foot on." Seest thou how what was done was opposed to the promise? Again He said, "In Isaac shall thy seed be called," and he believed: and again He says, Sacrifice to Me this one, who was to fill all the world from his seed. Thou seest the opposition between the commands and the promise? He enjoined things that were in contradiction to the promises, and yet not even so did the righteous man stagger, nor say he had been deceived.

He heard the opposite of the promises from Him who had made them; and yet he was not disturbed, but did them as if they had been in harmony therewith. For they were in harmony; being opposed indeed according to human calculations, but in harmony when viewed by Faith.