But thanks be to God! He gives us the victory through our Lord Jesus Christ.  1 Corinthians 15:57 NIV

The Lord your God goes with you; He will never leave you nor forsake you.  Deuteronomy 31:6 

Do not fear, for I am with you; do not be dismayed, for I am your God. I will strengthen you and help you.  Isaiah 41:10

With man this is impossible, but not with God; all things are possible with God. Mark 10:27

These verses teach us that a person who genuinely believes in Jesus is united to Him and kept forever.

We can have assurance because God is faithful. He’s taken upon Himself the project of bringing His sons and daughters to completion. We continue in faith because we are kept by grace. We persevere because God is preserving us. 

We as believers then simply, though not easily, must not let go of the Gospel. If we continue holding fast to “the faith,” we can rest assured that Christ is ours and we are His. That doesn’t mean we won’t sin, take a detour or wrong turn, or even that our faith is perfect and we never struggle with doubt. But seasons of struggling and having imperfect faith is set in contrast to willful unrepentance and rejection of Christ’s gospel.

Only those who repent of their sins - seek God, welcome Holy Spirit, trust Jesus - persevere for His kingdom while walking this place —endure in faith, and know Jesus Christ as the risen Saviour will enjoy God’s eternal rest. “Jesus said to the Jews who had believed Him, ‘If you abide in My word, you are truly My disciples’” (John 8:31). 

Endurance doesn’t save us, but it demonstrates our union with Christ. All those united to Jesus must persevere and will persevere, not because of the power of their faith but because of the preserving power and grace of He who is the object of their faith.

2 Thessalonians 1:3-4 NLT Dear brothers and sisters, we can’t help but thank God for you, because your faith is flourishing and your love for one another is growing.  We proudly tell God’s other churches about your endurance and faithfulness in all the persecutions and hardships you are suffering.

This should encourage us that if we hold fast to Jesus we’re promised salvation, not as something we earn but as the outcome of a faith that unites us to Jesus and receives all the promises in Him. It also warns anyone who has turned away from Jesus or seeks salvation apart from Him that there will be no grounds to think they will be saved.

There is no disconnect between God’s promise that He preserves and keeps all who are His and the truth that all who are His must persevere.