“Resist him, steadfast in the faith, knowing that the same sufferings are experienced by your brotherhood in the world.”
“Steadfast” means to make firm and solid. It is a military term meaning hold your order or keep a solid front. Secular Greek used “steadfast” for a close phalanx. The Greek phalanx was a body of heavily-armed infantry soldiers who formed ranks and files close and deep. The word carries the idea of solidity in mass and body. Soldiers had to maintain their ranks and formation, or the enemy would attack them from the side or from behind.
The Greek infantry divided into two main branches: the hoplitai and psiloi. The hoplitai were heavily armed troops arranged in phalanx. They were a body of 4,000 men drawn up in lines from eight to twenty-five deep. The psiloi were lightly armed troops, who carried out the skirmishing duties of the army, harassed the enemy, and hung around the flanks and rear of the phalanx with the cavalry in time of the battle.
The Christian should not break and run but hold his ground in the faith as a mighty phalanx of faith.
Steadfast comes to mean unbending. Christians should not bend their faith. They should deepen and strengthen their faith. Christians are to maintain their ranks in their faith. If they keep formation even though they undergo attack, together they will do something that they could not do alone.
Christians should not break and run. They should hold their ground. Their solid front and phalanx are the Word of God applied to their experiences.