The salvation of every believer is secure for all eternity from the moment of the new birth. The security is guaranteed by the fact that the life that is imparted is eternal life by the sealing ministry of the Holy Spirit.

Romans 8:1
Romans 8: 29-30
Romans 8 38-39
John 10: 27-30
Ephesians 1: 13-14
Ephesians 4: 30
Jude 1: 24