1Now there was a man of the Pharisees named Nicodemus, a member of the Jewish ruling council. 2He came to Jesus at night and said, "Rabbi, we know you are a teacher who has come from God. For no one could perform the miraculous signs you are doing if God were not with him."
3In reply Jesus declared, "I tell you the truth, no one can see the kingdom of God unless he is born again.[a]"
4"How can a man be born when he is old?" Nicodemus asked. "Surely he cannot enter a second time into his mother's womb to be born!" full story here