'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.

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 beloved brothers and sisters, be steadfast, immovable, always excelling in the work of the Lord [always doing your best and doing more than is needed], being continually aware that your labor [even to the point of exhaustion] in the Lord is not futile nor wasted [it is never without purpose].