Justin Martyr, First Apology 63

Even today, all Jews teach that the unnamed God spoke directly to Moses. The prophetic Spirit, speaking through the prophet Isaiah, rebukes them for this, just as we noted earlier: '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 they do not grasp what 'Father' and 'Son' mean. 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). The Word of God is that Son, as we have already said. He is also called Angel and Apostle, for he announces what must be known and is sent to proclaim what he announces—exactly as our Lord himself declared: 'Whoever hears me hears the one who sent me.' This point will become clear from the writings of Moses. Scripture records: 'An angel of God spoke to Moses in a flame of fire from the bush and said: I am the one who is, the God of Abraham, the God of Isaac, the God of Jacob, the God of your fathers. Go down to Egypt and lead out my people' (Exodus 3:2-4:17). You can learn the details that follow from those passages yourselves; it is not possible to write everything here. These words exist to prove that Jesus the Christ is the Son of God and an Apostle. He was the Word before all things, and he once appeared in the form of fire and again in an incorporeal image. Now, however, by God's will and for the sake of humanity, he became a man. He endured suffering at the hands of demons who incited senseless Jews against him—Jews who, despite having the plain statement in Moses: 'An angel of God spoke to Moses in a flame of fire in the bush and said: I am the one who is, the God of Abraham, the God of Isaac, the God of Jacob,' insist that the one who spoke was the Father of all, the Creator. Therefore the prophetic Spirit rebukes them again: 'Israel does not know me; my people do not understand.' Jesus also said to them, as we have shown: 'No one knows the Father except the Son, nor the Son except the Father, and those to whom the Son reveals him.' Jews have always assumed that the Father of all spoke to Moses, yet the one who spoke was the Son of God, who is also called Angel and Apostle. They are justly rebuked both by the prophetic Spirit and by Christ himself, because 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 the Father of all has a Son—the Word, the firstborn of God, who exists as God. Earlier he appeared to Moses and the other prophets through the form of fire and an incorporeal image. Now, in the era of your rule, as we said before, he became a man through a virgin by the Father's will, for the salvation of those who believe in him. He endured contempt and suffering so that by dying and rising he might conquer death. The words spoken to Moses from the bush—'I am the one who is, the God of Abraham, the God of Isaac, the God of Jacob, the God of your fathers'—signify that those patriarchs, though they died, remain alive and belong to Christ. They were the first of all humanity to seek God: Abraham fathered Isaac, Isaac fathered Jacob, just as Moses recorded.