In the book of Exodus chapter 3 we read about when God called Moses to lead the children of Israel out from under the oppression of the Pharaoh of Egypt. The following is the English translation of the Hebrew text Exodus 3:13,14 (KJB = King James Bible)
13 And Moses said unto God, Behold, when I come unto the children of Israel, and shall say unto them, The God of your fathers hath sent me unto you; and they shall say to me, What is his name? what shall I say unto them?
14 And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.