Genesis 22:1

Lend your ears here, you who have drawn near to God, you who believe yourselves to be faithful, and consider more diligently how the faith of the faithful is proved by these things that have been read to us. "And it came to pass," it says, "after these words, God tempted Abraham and said to him: Abraham, Abraham. And he said: here I am." Observe each and every thing that is written. For in each single thing, if someone knows how to dig deep, he will find a treasure, and perhaps even where it is not expected the precious jewels of the mysteries lie hidden. This man was formerly called Abram, and nowhere do we read that God called him by this name or said to him: Abram, Abram. For he could not be called by God by a name that was to be abolished, but he calls him by this name that He Himself had bestowed, and He does not only call him by this name, but even doubles it.

ON ABRAHAM. — The faith of this patriarch was so exceptional and wondrous that all other righteous people confess him, by God’s judgment, as the father of belief; nor is anyone worthy of and dear to God unless he is called his son. The right of his honor and value is faith, which he does not hesitate to give even to incredible things, and among other privileges he was also found worthy to see the Savior in hope of the future Incarnation, as the Lord said and proved to the Jews: Your father Abraham rejoiced that he might see my day; and he saw it and was glad (Jn. 8:56). For since he became father by the value of faith, it was fitting that he should foresee the hope of his future children, which, through the gracious and provident God, would overflow from a human and devout father upon his obedient sons as an inheritance. Let us now see what this faith believed, so that it reached such honor and glory by divine judgment. We have praised the faith, but we have not yet said what it believed. For the Lord, leading him out, showed him the stars of heaven and said: If you can, number them. So shall your seed be. And Abraham believed God, and it was reckoned to him as righteousness (Gen. 15:5–6). It would not be a great thing to have believed God, except that what he believed the world judges not to be believed and as foolish, because this is not within the hope of things according to nature. Therefore Abraham, being one out of the world because he believed this, was separated from worldly people and justified. Therefore, believing this is made great by the unbelieving wisdom of the world, and to have believed against its hope is of the highest value. For the despair of worldly men is the value and hope of Christians. For the cause of evil becomes the reward of good: faith is stronger and fuller when it commits itself more to things that are incredible. A man already dried up and from an aged wife believed he would have seed so abundant that it could not be numbered; looking not so much at what was shown, but at him who showed it, not thinking that he could lie. And therefore it was counted to him for righteousness. For it is dull to believe a thing absurd and known to be impossible, unless there is a person who persuades us to believe it. Therefore Abraham is admirable for his faith and for the discernment of his heart, since he both believes that which is incredible and commits himself to him to whom not to believe is both foolish and dangerous. This shows our faith to be reasonable, that it believes this not of any other than of God, that he is able to do what he promises. This, then, is the bulwark of faith, this its triumph. Seeing this, some wise men of the world, because the nature of things cannot do this, say it is foolish to believe. Ignorant that, according to the Apostle, what is foolish of God is wiser than men (1 Cor. 1:25). For they would rightly judge us foolish if we believed of the nature of things what is proved not to be possible. But we, on the contrary, believe that God will be able to do what nature cannot, if he has promised it. What folly can be found in this matter? If, however, the work which is believed possible is unworthy of God, then faith is rightly compared to dullness; but if it is worthy, precisely because it is impossible to the creature, why is the faith not to be praised which attributes so much to the Creator as the creature is denied power to do? Great and admirable, then, is Abraham, who did not doubt to believe God against the world’s judgment, because he can do what he promises. A Chaldean by birth, he appears as a master of belief: though skilled in astrology, he still placed God above human counsel, judging it fitting that such things be believed of God as cannot be investigated in respect to how they may come to pass. For he strengthened his own weakness by the power of God, since God determined, to proclaim the unique greatness of his majesty, to perform things that are impossible and unheard of to the world; and by doing this he would show himself Lord of the creature, and the creature would subject itself to him whose work would seem impossible to all others; by whose unbelief the most faithful Abraham is raised higher. For his faith is the punishment of unbelievers; the deceit of unbelievers is his glory. For he is the father of the faithful and the judge of the unfaithful. By his example, the good are granted eternal life, and the wicked will receive eternal punishments. In that time, when the world was still small in knowledge and not yet enlightened by signs and wonders that might draw it to faith, he did not deny faith to God against his own understanding. Therefore holy Abraham was given as a most faithful example to the human race. In him all nations were prefigured as coming to salvation through faith; and that the overflowing increase of his faith might be known, he is tested and ordered to sacrifice his son to God, a thing that had never before been done, and he is neither disturbed by the novelty of the deed nor does he dispute whether a murder ought to be committed at God’s command, he who had threatened that murder must not be committed. Therefore, fearless and secure about the will of God, he does not hesitate to think that what God commands is provident: and this son, whom two old people received through a promise, the reward of faith, the witness of virtues, and in whom all hope of the promised future seed was held. That he might fulfill this with complete devotion, he did not tell his mother, lest she bring some obstacle to his obedience, knowing that mothers are the more inclined in love toward the affection they bear for their children; therefore he concealed it from her, not doubting that what God commands must be fulfilled, so that by this example we might be taught to carry out God’s commands with all carefulness. For if the most faithful Abraham is found obedient in a matter so grave and harsh, how much more should we, to whom things are commanded that can be accepted? O faith dedicated to God, and hope firm in the Lord, which is so dear and sweet that it is preferred to the affections of parents and children, as Scripture says: Taste and see, that the Lord is sweet (Ps. 33:9)! But our patriarch, most faithful Abraham, because he was a prophet, knew what was to follow. Therefore, in accordance with what the Lord had just said, he then acted, so that he preferred God in love over his son, dear as he was, with the Lord saying, “If anyone loves father or mother, or children more than me, he is not worthy of me” (Matt. 10:37). Therefore the Patriarch, in order to be found worthy of the Lord above all others, did not refuse even to kill his son.

A familiar example is Abraham's "trial" when he was ordered to sacrifice Isaac. With the historicity or the morality of that story I am not now concerned, but with the obvious question "If God is omniscient He must have known what Abraham would do, without any experiment; why, then, this needless torture?" But as St. Augustine points out, whatever God knew, Abraham at any rate did not know that his obedience could endure such a command until the event taught him: and the obedience which he did not know that he would choose, he cannot be said to have chosen. The reality of Abraham's obedience was the act itself; and what God knew in knowing that Abraham "would obey" was Abraham's actual obedience on that mountain top at that moment. To say that God "need not have tried the experiment" is to say that because God knows, the thing known by God need not exist.