Why must a sinner be born again?

Spiritual rebirth, as Jesus explains in John 3:6-7, is essential for entering the Kingdom of God. Without being born again, a person cannot understand or accept the things of the Spirit, as emphasized in 1 Corinthians 2:14. This new birth is the work of the Holy Spirit, who transforms the heart and enables the sinner to respond to the gospel with faith. Just as physical birth cannot be willed or accomplished by the individual, the new birth is through God's sovereign grace, making it clear that salvation is a divine act rather than a human decision.