"So, then, brothers, stand firm and maintain your hold on the traditions that you were taught, whether it was through a verbal message or through a letter of ours." (2 Thess 2:15).
STEADFAST UNDER TEST.
'That is the way to be immovable in the midst of troubles, as a rock amidst the waves. When God is in the midst of a kingdom or city, He makes it firm as Mount Zion, that cannot be removed. When He is in the midst of a soul, though calamities throng about it on all hands, and roar like the billows of the sea, yet there is a constant calm within, such a peace as the world can neither give nor take away. What is it but want of lodging God in the soul, and that in His stead the world is in men's hearts, that makes them shake like leaves at every blast of danger?' (R. Leighton).
"Remember: 'We count those happy who stood firm.' You have all heard how Job stood firm, and you have seen how the Lord treated him in the end. For the Lord is full of pity and compassion." (James 5:11 NEB).
"Consequently, my beloved brothers, become steadfast, unmovable, always having plenty to do in the work of the Lord, knowing that your labour is not in vain in connection with the Lord." (1 Cor 15:58).
(1) STEADFAST: Established, constant, resolute.