The answer to the question "How can a man be born when he is old?" is – When he is old enough to die – to die right out to his "rag rights," to his virtues, to his religion, to everything, and to receive into himself the life which never was there before. The new life manifests itself in conscious repentance and unconscious holiness.
"As many as received Him." (John 1:12.) Is my knowledge of Jesus born of internal spiritual perception, or is it only what I have learned by listening to others? Have I something in my life that connects me with the Lord Jesus as my personal Saviour? All spiritual history must have a personal knowledge for its bedrock. To be born again means that I see Jesus.
"Except a man be born again, he cannot see the kingdom of God." (John 3:3.) Do I seek for signs of the Kingdom, or do I perceive God’s rule? The new birth gives a new power of vision whereby I begin to discern God’s rule. His rule was there all the time, but true to His nature; now that I have received His nature I can see His rule.
"Whosoever is born of God doth not commit sin." (1 John 3:9.) Do I seek to stop sinning or have I stopped sinning? To be born of God means that I have the supernatural power of God to stop sinning. In the Bible it is never – Should a Christian sin? The Bible puts it emphatically - A Christian must not sin. The effective working of the new birth life in us is that we do not commit sin, not merely that we have the power not to sin, but that we have stopped sinning. 1 John 3:9 does not mean that we cannot sin; it means that if we obey the life of God in us, we need not sin.