Genesis 22:17

In the former promise there was only the statement; here an oath is interposed, which the holy apostle writing to the Hebrews interprets in this way, saying, "God, meaning to show the heirs of the promise the immutability of his counsel, interposed an oath." And again, Scripture says, "Men swear by one greater than themselves." "But God, because he had no one greater by whom he might swear," " 'I swear by myself,' said the Lord." It was not that necessity forced God to swear (for who would exact the oath from him?), but as the apostle Paul has interpreted it, that by this he might point out to his worshipers "the immutability of his counsel." So also elsewhere it is said by the prophet, "The Lord has sworn nor will he repent: You are a priest forever according to the order of Melchizedek."12At that time in the first promise there is no reason stated why the promise is given, only that he brought him forth and "showed him," Scripture says, "the stars of heaven, and said, 'So shall your seed be.' " But now he adds the reason on account of which he confirms with an oath the promise which will be steadfast. For he says, "Because you have done this thing and have not spared your son." He shows therefore that because of the offering or passion of the son the promise is steadfast. This clearly points out that the promise remains steadfast because of the passion of Christ for the people of the Gentiles "who are of the faith of Abraham."

It is written in the prophet speaking in the person of the Lord, "I have used similitudes by the ministries of the prophets." What this statement means is this: Although our Lord Jesus Christ is one in his substance and is nothing other than the Son of God, nevertheless he is represented as various and diverse in the figures and images of the Scripture.For example, as I recall we have explained in what precedes that Christ himself was Isaac, in type, when he was offered as a holocaust. Nevertheless the ram also represented him. I say furthermore that he is exhibited also in the angel who spoke to Abraham and says to him, "Lay not your hand on the boy." For he says to him, "Because you have done this thing, I will certainly bless you." He is said to be the sheep or the lamb that is sacrificed in the Passover, and he is designated as the shepherd of the sheep. He is also described, no less, as the high priest who offers the sacrifice.

What person now needs an explanation to know how the seed of Christ is multiplied who sees the preaching of the gospel extended from the ends of the earth "to the ends of the earth"? And who sees that there is now almost no place which has not received the seed of the Word? For indeed this also was prefigured in the beginnings of the world when God said to Adam, "Increase and multiply."

The bonds indeed with which they bind us are our passions and vices with which we are bound until "we crucify our flesh with the vices and concupiscences" and so at last "break their bonds asunder and cast away their yoke from us."47The seed of Abraham, therefore, that is, the seed of the Word, which is the preaching of the gospel and faith in Christ, has occupied "the cities of their enemies."

To be able to find [these treasures], we need the help of God who alone can "break in pieces the doors of bronze" by which they are shut up and hidden and who "cuts asunder the bars of iron" and the bolts by which access was prohibited for attaining all the truths that were written and hidden in Genesis. [These truths are] concerning the different kinds of souls, concerning the seeds and generations that either pertain directly to Israel or are separated much further from his offspring.