Exodus 3:6

And all the Jews even now teach that the nameless God spake to Moses; whence the Spirit of prophecy, accusing them by Isaiah the prophet mentioned above, said “The ox knoweth his owner, and the ass his master’s crib; but Israel doth not know Me, and My people do not understand.” And Jesus the Christ, because the Jews knew not what the Father was, and what the Son, in like manner accused them; and Himself said, “No one knoweth the Father, but the Son; nor the Son, but the Father, and they to whom the Son revealeth Him.” Now the Word of God is His Son, as we have before said. …

1. Having now briefly arranged these points in order as we best could, it follows that, agreeably to our intention from the first, we refute those who think that the Father of our Lord Jesus Christ is a different God from Him who gave the answers of the law to Moses, or commissioned the prophets, who is the God of our fathers, Abraham, Isaac, and Jacob. For in this article of faith, first of all, we must be firmly grounded. We have to consider, then, the expression of frequent recurrence in the Gospels, and subjoined to all the acts of our Lord and Saviour, “that it might be fulfilled which was spoken by this or that prophet,” it being manifest that the prophets are the prophets of that God who made the world. From this therefore we draw the conclusion, that He who sent the prophets, Himself predicted what was to be foretold of Christ. …

2. Now they seek to exhibit the foundation for their dogma by citing the word in the law, “I am the God of your fathers: ye shall have no other gods beside me;” and again in another passage, “I am the first,” He saith, “and the last; and beside me there is none other.” Thus they say they prove that God is one. And then they answer in this manner: “If therefore I acknowledge Christ to be God, He is the Father Himself, if He is indeed God; and Christ suffered, being Himself God; and consequently the Father suffered, for He was the Father Himself.” But the case stands not thus; for the Scriptures do not set forth the matter in this manner. But they make use also of other testimonies, and say, Thus it is written: “This is our God, and there shall none other be accounted of in comparison of Him. …

In Joel: “Blow with the trumpet in Sion; sanctify a fast, and call a healing; assemble the people, sanctify the Church, gather the elders, collect the little ones that suck the breast; let the Bridegroom go forth of His chamber, and the bride out of her closet.” Also in Jeremiah: “And I will take away from the cities of Judah, and from the streets of Jerusalem, the voice of the joyous, and the voice of the glad; the voice of the bridegroom, and the voice of the bride.” Also in the eighteenth Psalm: “And he is as a bridegroom going forth from his chamber; he exulted as a giant to run his course. From the height of heaven is his going forth, and his circuit even to the end of it; and there is nothing which is hid from his heat.” Also in the Apocalypse: “Come, I will show thee the new bride, the Lamb’s wife. …

XXX . Do not therefore keep any such observances about legal and natural purgations, as thinking you are defiled by them. Neither do you seek after Jewish separations, or perpetual washings, or purifications upon the touch of a dead body. But without such observations assemble in the dormitories, reading the holy books, and singing for the martyrs which are fallen asleep, and for all the saints from the beginning of the world, and for your brethren that are asleep in the Lord, and offer the acceptable Eucharist, the representation of the royal body of Christ, both in your churches and in the dormitories; and in the funerals of the departed, accompany them with singing, if they were faithful in Christ. …

Further, we have to ask in what sense He is called in the Apocalypse the First and the Last, and how, in His character as the First, He is not the same as the Alpha and the beginning, while in His character as the Last He is not the same as the Omega and the end. It appears to me, then, that the reason able beings which exist are characterized by many forms, and that some of them are the first, some the second, some the third, and so on to the last. To pronounce exactly, however, which is the first, what kind of a being the second is, which may truly be designated third, and to carry this out to the end of the series, this is not a task for man, but transcends our nature. We shall yet venture, such as we are, to stand still a little at this point, and to make some observations on the matter. …

23. But when Moses was sent to lead the children of Israel out of Egypt, it is written that the Lord appeared to him thus: “Now Moses kept the flock of Jethro his father-in-law, the priest of Midian: and he led the flock to the back side of the desert, and came to the mountain of God, even to Horeb. And the Angel of the Lord appeared unto him in a flame of fire, out of the midst of a bush; and he looked, and, behold, the bush burned with fire, and the bush was not consumed. And Moses said, I will now turn aside, and see this great sight, why the bush is not burnt. And when the Lord saw that he turned aside to see, God called unto him out of the midst of the bush, and said, I am the God of thy father, the God of Abraham, the God of Isaac, and the God of Jacob.” He is here also first called the Angel of the Lord, and then God. …

20. But because these things are known to men, in that they are done by men, they may well meet with reverence as being holy things, but they cannot cause wonder as being miracles. And therefore those things which are done by angels are the more wonderful to us, in that they are more difficult and more known; but they are known and easy to them as being their own actions. An angel speaks in the person of God to man, saying, “I am the God of Abraham, and the God of Isaac, and the God of Jacob;” the Scripture having said just before, “The angel of the Lord appeared to him.” And a man also speaks in the person of God, saying, “Hear, O my people, and I will testify unto thee, O Israel: I am the Lord thy God.” A rod was taken to serve as a sign, and was changed into a serpent by angelical power; but although that power is wanting to man, yet a stone was taken also by man for a similar sign. …

41. Besides this wonderful agreement between the types and the things typified, the adversary may be convinced by plain prophetic intimations, such as this: "In thy seed shall all nations be blessed." This was said to Abraham, and again to Isaac, and again to Jacob. Hence the significance of the words "I am the God of Abraham, and Isaac, and Jacob." God fulfills His promise to their seed in blessing all nations. With a like significance, Abraham himself, when he made his servant swear, told him to put his hand under his thigh; for he knew that thence would come the flesh of Christ, in whom we have now, not the promise of blessing to all nations, but the promise fulfilled.

7. He that is born of the Catholic Church, is born, as it were, of Sarah, of the free woman; he that is born of heresy is, as it were, born of the bond woman, but of Abraham’s seed. Consider, beloved, how great a mystery. God testifies, saying, “I am the God of Abraham, and the God of Isaac, and the God of Jacob.” Were there not other patriarchs? Before these, was there not holy Noah, who alone of the whole human race, with all his house, was worthy to be delivered from the flood, he in whom, and in his sons, the Church was prefigured? Borne by wood, they escaped the flood. Then afterwards great men whom we know, whom Holy Scriptures commends, Moses faithful in all his house. …

2. Spiritual regeneration is one, just as the generation of the flesh is one. And Nicodemus said the truth when he said to the Lord that a man cannot, when he is old, return again into his mother’s womb and be born. He indeed said that a man cannot do this when he is old, as if he could do it even were he an infant. But be he fresh from the womb, or now in years, he cannot possibly return again into the mother’s bowels and be born. But just as for the birth of the flesh, the bowels of woman avail to bring forth the child only once, so for the spiritual birth the bowels of the Church avail that a man be baptized only once. …

13. But those men, indignant, yet dead, and predestinated to death eternal, answered with insults, and said, “Now we know that thou hast a devil. Abraham is dead, and the prophets.” But not in that death which the Lord meant to be understood was either Abraham dead or the prophets. For these were dead, and yet they live: those others were alive, and yet they had died. For, replying in a certain place to the Sadducees, when they stirred the question of the resurrection, the Lord Himself speaks thus: “But as touching the resurrection of the dead, have ye not read how the Lord said to Moses from the bush, I am the God of Abraham, and the God of Isaac, and the God of Jacob? He is not the God of the dead, but of the living.” If, then, they live, let us labor so to live, that after death we may be able to live with them. …