Because God gives us eternal life through Jesus Christ, the true believer is secure in that salvation for eternity. If you have been genuinely saved, you cannot lose it. Salvation is maintained by the grace and power of God, not by the self-effort of the Christian. It is the grace and keeping power of God that gives us this security.

John 10:29 - "My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father's hand.

2 Tim 1:12 - For this reason I also suffer these things, but I am not ashamed; for I know whom I have believed and I am convinced that He is able to guard what I have entrusted to Him until that day.

Heb 7:25 - Hence, also, He is able to save forever those who draw near to God through Him, since He always lives to make intercession for them.

Heb 10:10-14 - By this will we have been sanctified through the offering of the body of Jesus Christ once for all. And every priest stands daily ministering and offering time after time the same sacrifices, which can never take away sins; but He, having offered one sacrifice for sins for all time, sat down at the right hand of God, waiting from that time onward until His enemies be made a footstool for His feet. For by one offering He has perfected for all time those who are sanctified.

1 Pet 1:3-5 - Blessed be the God and Father of our Lord Jesus Christ, who according to His great mercy has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead, to obtain an inheritance which is imperishable and undefiled and will not fade away, reserved in heaven for you, who are protected by the power of God through faith for a salvation ready to be revealed in the last time.