Your friend is absolutely wrong. Matthew 3:16-17 says, 'When He had been baptized, Jesus came up immediately from the water; and behold, the heavens were opened to Him, and He saw the Spirit of God descending like a dove and alighting upon Him. And suddenly a voice came from heaven, saying,'This is My beloved Son, in whom I am well pleased.'' In this narrative we see a man standing in the Jordan River, a voice speaking out of the sky, and a likeness of a dove descending from the sky. Please ask your friend if he really believes that anyone reading the Bible for the first time would draw the conclusion from this passage that the Creator of all things is three distinct divine persons.