Your whole point depends on one passage from Paul. But Jesus is the One who gives the truth of salvation, and Jesus never said that a person is automatically guaranteed heaven the moment they believe. He never said that repentance is not part of the gospel. In fact, Jesus preached repentance from the very beginning. “Repent ye, for the kingdom of heaven is at hand” (Matthew 4:17 ). His apostles preached the same message. Peter said “Repent ye, and be baptized… unto the remission of your sins” (Acts 2:38). So repentance is part of the good news, not something to throw away.
Jesus taught that the Father gives the Spirit to those who obey Him and ask Him (Luke 11:13 ). He never said the Spirit is a guarantee no matter how a person lives. Jesus warned that a branch in Him can be cut off if it stops bearing fruit (John 15:2 ). If salvation were a guaranteed gold seal, Jesus would not warn His own disciples like that.
Jesus also said “Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven but he that doeth the will of my Father” (Matthew 7:21 ). If entrance were guaranteed by one moment of belief, Jesus would not say this. He also said “He that endureth to the end, the same shall be saved” (Matthew 24:13). Endurance is not automatic, it is a daily walk with Christ.
So how should a person behave if they truly believe in Jesus? Jesus answered it Himself. A true disciple keeps His word (John 8:31 ), loves God and neighbor (Matthew 22:37 to 39) , forgives others to be forgiven (Matthew 6:14 to 15 ), turns from sin (John 8:11 ), and walks in the light (John 12:35 to 36 ). This is the life of someone saved by God’s grace.
Jesus never promised a sealed, unconditional future. He promised eternal life to those who follow Him and remain in His word.
That is the truth He taught.
You have thoroughly confused the free gift of salvation with your behavior in you Christian life.
Romans 6:23
For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Salvation is a free gift given to those who believe in the death and resurrection of Jesus.
Ephesians 2:8
For by grace you have been saved through faith; and that not of yourselves, it is the gift of God.
Stop polluting the gospel of Jesus Christ with your filthy works and your obedience to the law.
Salvation always remains a free gift and cannot be earned.