Nicodemus searched for the truth. He made an appointment with Jesus to ask the tough questions. Nicodemus wanted spiritual answers and Jesus spoke to him in earthly terms that had spiritual significance. Jesus spoke of being born again. Nicodemus tried to put that in earthly terms of entering your mother’s womb to be born again. It didn’t make sense to him. Jesus said, “What is flesh is flesh and what is spirit if spirit. You must be born again.” Just as one has a physical birth one must also have a spiritual birth.
When you are born physically you are a helpless baby unable to do anything for yourself, but you grow and mature to adulthood. When you have a spiritual birthday, you begin as a helpless baby but you grow and mature through reading the Scriptures, hearing biblical teaching, prayer and you want to become a mature Christian.
John 3:16 For God so loved the world that he gave his only begotten Son that whosoever believes in him should not perish but have everlasting life.