You’re asking about a line from this passage, Exodus 3:13-14: "Then Moses said to God, ’If I come to the people of Israel and say to them ’The God of your fathers has sent me to you,’ and they ask me ’What is his name?’ what shall I say to them?’ God said to Moses ’I AM who I AM.’ And he said, ’Say this to the people of Israel: I AM has sent me to you’" (RSV).
Moses is being guided and charged by the Lord of his being—the Presence of God within him that the New Testament would later describe as the Christ. There is no need for an outside reference and no need to link his guidance with any previous conception of God. He is being told, in essence, to claim his own personal expression of God as his Source. There is great creative power in the phrase "I AM." Jesus later affirms the same lesson through his great "I AM" statements in the Gospel of John. "I AM" is the way we connect directly with the indwelling Presence within us, which is why we must be careful about how we use the words. "I AM" affirms and evokes the Power of God that is our true identity; and the words we place after "I AM" define how we choose to express that Power in the world.