“Jesus answered and said to him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.” He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him.” John 3:3, 36 LSB https://bible.com/bible/3345/jhn.3.3-36.LSB
What does it mean to be a Christian and therefore receive God’s reward of eternal life in heaven now and upon the new earth when He remakes the universe, and all that is in it to dwell with His holy people as He is holy who have been made holy through the righteousness of Jesus appropriated to them by faith in His life from heaven, death on the cross, and resurrection from the dead? We cannot be born Christian. We must be born again. No good behavior, no baptism, no Christian schooling, nothing will save a person except faith in the life of Jesus perfectly lived before God so that He could offer Himself a perfect sacrifice for the sins of all humanity. This perfect life was crucified by men as a sacrifice by God for the punishment of all the evil all men have ever done since our birth. Risen from the dead, justified by God, Jesus the Judge now pardons all who come to Him by faith, believing He alone, by His work alone, can alone forgive men for all eternity for their sins. This belief in the work of Jesus appropriated to those who believe in Jesus is manifest by the people of Jesus in obedience to all the commands of Jesus. The person truly born again is characterized by obedience to everything Jesus commands, as recorded in the Scriptures. The man who says he is a Christian but does not live as Jesus did, seeking God and seeking to do God’s will, deceives himself. We know for certain we are born again when we love God and do His will, believing that all the work God requires of us has been accomplished by Jesus and appropriated to us by faith in Him.