Justin Martyr, First Apology 63

Jews still teach today that the unnamed God spoke to Moses. The prophetic Spirit, speaking through the prophet Isaiah mentioned earlier, rebukes them with words we have already cited: "An ox knows its owner, and a donkey its master's manger, but Israel does not know me; my people do not understand" (Isaiah 1:3). Jesus the Christ likewise rebuked them because the Jews did not know what a Father is or what a Son is. He said, "No one knows the Father except the Son, and no one knows the Son except the Father and those to whom the Son chooses to reveal him" (Matthew 11:27). As we have said before, the Word of God is His Son. He is also called an angel and an apostle, because He announces what must be known and is sent to declare what He announces, just as our Lord Himself said: "Whoever hears me hears the one who sent me" (Matthew 10:40). This will also become clear from the writings of Moses. For it says there: "An angel of the Lord appeared to Moses in a flame of fire from within a bush... 'I am the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob.'... So now, go. I am sending you to Pharaoh to bring my people the Israelites out of Egypt" (Exodus 3:2, 6, 10). If you wish to learn the details that follow from those writings, you are able to do so; it is not possible to record everything here. These words exist as proof that Jesus the Christ is the Son of God and apostle, existing before as the Word. He appeared at one time in the form of fire and at another in an incorporeal image. Now, however, by the will of God, He became a man for the sake of the human race. He endured and suffered what the demons, working through the senseless Jews, brought upon Him. Even though the Jews have it expressly written in the books of Moses—"An angel of the Lord appeared to him in flames of fire from within a bush... 'I am the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob'" (Exodus 3:2, 6)—they claim that the one who spoke these things is the Father of all. Therefore the prophetic Spirit rebukes them: "But Israel does not know me, my people do not understand" (Isaiah 1:3). And again Jesus, as we have shown, would say to them: "No one knows the Father except the Son, and no one knows the Son except the Father and those to whom the Son chooses to reveal him" (Matthew 11:27). The Jews have always assumed that the Father of all spoke to Moses, but the one who spoke was actually the Son of God, who is also called an angel and apostle. Therefore they are justly rebuked both by the prophetic Spirit and by Christ Himself, for they know neither the Father nor the Son. Those who claim the Son is the Father are rebuked for knowing neither the Father nor the fact that He is the Son of the Father of all—He who is the Word and the firstborn of God and exists as God. He previously appeared to Moses and the other prophets through the form of fire and an incorporeal image. But now, in the times of your rule, as we said before, He became a man through a virgin according to the Father's will for the salvation of those who believe in Him. He endured being despised and suffering, so that by dying and rising He might conquer death. The words spoken to Moses from the bush—"I am the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob" (Exodus 3:6)—signify that even though those patriarchs died, they remain alive and are Christ's people. For they were the first of all humanity to devote themselves to seeking God: Abraham begot Isaac, Isaac begot Jacob, as Moses also wrote.