John Chrysostom

"And in nothing affrighted by the adversaries; which is for them an evident token of perdition, but to you of salvation." Well said he, "affrighted," this is what befalls us from our enemies, they only frighten. "In nothing" therefore, he says, whatever happens, whether dangers-whether plots. For this is the part of those who stand upright; the enemy can do nought but frighten only. …

Homily on Philippians 4 ↗

Theophylact of Ohrid

I do not say, he writes, simply: do not waver, but also do not be frightened, that is, do not be troubled by anything, even if they threaten you with danger, or frighten you with death; for they can do nothing, only threaten — so weak are they. When they see that all their countless machinations are unable to frighten you, will they not consider this a clear proof that their cause will perish, while yours will remain firm and indestructible, and at the same time salvific.

Commentary on Philippians ↗

Thomas Aquinas

Secondly, he expects constancy: and not frightened in anything by your opponents. First, he urges them to be brave, because their opponents can do only as much as God allows: "But not a hair of your head will perish" (Lk. 21:18); "Its leaf does not wither" (Ps. 1:3); "Who are you that you are afraid of man who dies, of the son of man who is made like grass?" (Is. 51:12). There are three reasons for this: the first is taken from the fruit of tribulation. …

Commentary on Philippians ↗