Jesus spoke to Nicodemus in John 3:
There are at least 3 interpretations:
3. Water refers to natural watery birth (amniotic sac breaking), John 3:
Spirit || human spirit
Because of the immediate context and parallelisms, I think #3 is the best interpretation.
See also What does it mean to be born again?.
What is born of water?5 Jesus answered, “Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit.
There are at least 3 interpretations:
- Water is a symbol of cleansing, Ezekiel 36:
2. Water refers to John's water baptism, John 1:25 “Then I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your filthiness and from all your idols. 26“Moreover, I will give you a new heart and put a new spirit within you; and I will remove the heart of stone from your flesh and give you a heart of flesh. 27“I will put My Spirit within you and cause you to walk in My statutes, and you will be careful to observe My ordinances. 28“You will live in the land that I gave to your forefathers; so you will be My people, and I will be your God.
Nicodemus knew about John's water baptism for repentance. Jesus informed him that there was another requirement. Ellicott, Cambridge Bible, and Bengel agreed to this interpretation #2.33 And I myself did not know him, but the one who sent me to baptize with water told me, ‘The man on whom you see the Spirit come down and remain is the one who will baptize with the Holy Spirit.’
3. Water refers to natural watery birth (amniotic sac breaking), John 3:
water || human flesh3 Jesus replied, “Very truly I tell you, no one can see the kingdom of God unless they are born again.”
4 “How can someone be born when they are old?” Nicodemus asked. “Surely they cannot enter a second time into their mother’s womb to be born!”
5 Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. 6 That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.
Spirit || human spirit
Because of the immediate context and parallelisms, I think #3 is the best interpretation.
See also What does it mean to be born again?.