What does John 1:13 mean?
This is John's first mention of being "born" into the kingdom of God. The term "born again" has become a cliché, and many people misunderstand it. The term is important because of what it implies.When a child is born, virtually all effort, energy, and pain is endured by the mother, not the child. She changes very little. And yet, the child experiences a great deal of change. Salvation is much the same: God's pain and effort result in our benefit. He, of course, does not change at all in the process; but those who are saved change greatly. Saying that this does not occur "of blood" means it is not a natural occurrence. Saying that it is not "of the will of the flesh" means it is not a matter of human decisions. This rebirth is entirely the work of God, and according to His will (Ephesians 1:5). Our salvation is not dependent on anything in our human nature. This is good, because if it were, we'd all be lost forever (Titus 3:4–5)!
Jesus will clarify this concept during His conversation with Nicodemus, in John chapter 3.