Revelation 1:8 says:
8The Lord God says, "I am the Alpha and the Omega. I am the One who is, who [always] was, and who is coming. I am the All-Powerful." (Easy-to-Read Version)
King James Version: 8I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.