Nicodemus was a high-ranking Pharisee who recognized Jesus as someone special, and wanted to understand more. Immediately, Jesus dives straight in and tells him that he must be born again.
Nicodemus then asks for clarification, and Jesus then explains that he is talking about spiritual birth. He says that no-one can enter the kingdom of God unless he is born of water and the Spirit. The water symbolises cleansing from sin, and the Spirit (or breath of God) gives life.
He then points out that you can’t see the wind, but you can see the effects of the wind, and similarly, you can’t see the Spirit, but you can see the effects of the Spirit. (John 3:1-8)
In the early church, they quickly realised that becoming a Christian and receiving the Holy Spirit were inextricably linked. For example, evidence of the Spirit’s power in the Gentiles in Cornelius’s house
convinced Peter that the Gospel really was for Gentiles as well as Jews. (Acts 10:46-48)
A baby does not get any choice about being born, and is helpless. In a similar way, we do not really decide to become Christians, it is an act of God (John 1:12-13).
Does belief come first or rebirth? Do we come to the decision to put our faith in Jesus, or has God led us to that point?
Jesus said “No-one comes to me unless the Father who sent me draws him” (John 6:44)
So, God has done everything for us, and none of it is our doing. If we choose to believe in Him, it is because He chose us.