'Firmness' in the Bible

These were the heads of their fathers’ households: Epher, Ishi, Eliel, Azriel, Jeremiah, Hodaviah, and Jahdiel, warriors of valor [willing and able to encounter danger], famous men, and heads of the households of their fathers.

and worthless (unprincipled, unethical) men gathered around him, useless and wicked men, who proved too strong for Rehoboam the son of Solomon when Rehoboam was young and timid, and could not assert himself against them.

And as you saw the feet and toes, partly of potter’s clay and partly of iron, it will be a divided kingdom; but there will be in it some of the durability and strength of iron, just as you saw the iron mixed with common clay.

For even though I am absent [from you] in body, nevertheless I am with you in spirit, delighted to see your good discipline [as you stand shoulder to shoulder and form a solid front] and to see the stability of your faith in Christ [your steadfast reliance on Him and your unwavering confidence in His power, wisdom, and goodness].