We know we must be born again because Jesus explicitly states it in John 3:3, declaring it as the only way to see the kingdom of God.
The necessity of being born again is a fundamental doctrine highlighted in John 3:3, where Jesus tells Nicodemus that except a man be born again, he cannot see the kingdom of God. This is a clear and direct statement that emphasizes the urgency and exclusivity of spiritual rebirth. In Reformed theology, this aligns with the belief that regeneration is a work solely of the Holy Spirit. It cannot be achieved by human effort or will, as indicated by verses like John 1:12-13, which state that being born again is not by blood or the will of man, but of God. Thus, the acknowledgment that one must be born again rests upon the authority of Scripture and the teaching of Christ Himself.
Commentary