Jesus did not become a man. Jesus was a man. Was born a man.
Jesus existed as God before He took on human form. He existed in heaven prior to becoming a human being. Who do you think Abraham was speaking to before He sent His angels to destroy Sodom and Gomorrah and the surrounding towns?
"Therefore the Lord Himself will give you a sign: Behold, the virgin will be with child and will give birth to a son, and will call Him Immanuel."
Immanuel means 'God with us.'
