3:14 be lifted up. The means by which the new birth and the promised kingdom could be made effectual was the “lifting up” of the Son of man in a way analogous to the manner in which Moses lifted up the brasen serpent in the wilderness (Numbers 21:5-9). The dying Israelites who, by faith, would simply look on the impaled serpent (symbolizing judgment on their sins) would be healed of the deadly poison in their bodies and live.
3:15 should not perish. In comparison, if any lost sinner would merely look in faith to the Lord Jesus, “lifted up” (John 12:32) to die in judgment for his sins on the cross, he also will not only not die, but will receive eternal life. If “ye must be born again,” then “even so must the Son of man be lifted up.” Genuine saving faith, therefore, involves belief in the deity of Christ (John 3:13) and His substitutionary death (John 3:14). It will then result in the new birth (John 3:7-8) and everlasting life (John 3:15).