'Steadfast' in the Bible

And He will also confirm you to the end [keeping you strong and free of any accusation, so that you will be] blameless and beyond reproach in the day [of the return] of our Lord Jesus Christ.

But he who stands steadfast in his heart, having no necessity, but has power over his own heart, to keep his own virgin, does well.

Therefore let the one who thinks he stands firm [immune to temptation, being overconfident and self-righteous], take care that he does not fall [into sin and condemnation].

Therefore, my dear brothers, be steadfast, immovable, always excelling in the Lord’s work, knowing that your labor in the Lord is not in vain.