Romans 4:19–21 19 He did not weaken in faith when he considered his own body, which was as good as dead (since he was about a hundred years old), or when he considered the barrenness of Sarah’s womb. 20 No unbelief made him waver concerning the promise of God, but he grew strong in his faith as he gave glory to God, 21 fully convinced that God was able to do what he had promised.
1 Timothy 6:12 12 Fight the good fight of the faith. Take hold of the eternal life to which you were called and about which you made the good confession in the presence of many witnesses.
Colossians 1:21–23 21 And you, who once were alienated and hostile in mind, doing evil deeds, 22 he has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him, 23 if indeed you continue in the faith, stable and steadfast, not shifting from the hope of the gospel that you heard, which has been proclaimed in all creation under heaven, and of which I, Paul, became a minister.
Hebrews 3:12–14 12 Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. 13 But exhort one another every day, as long as it is called “today,” that none of you may be hardened by the deceitfulness of sin. 14 For we have come to share in Christ, if indeed we hold our original confidence firm to the end.