A.T. Robertson Commentary 1 Thessalonians 5:8

"But let us, since we are of the day, be sober, putting on the breastplate of faith and love; and for a helmet, the hope of salvation." — 1 Thessalonians 5:8 (ASV)

Putting on the breastplate of faith and love (ενδυσαμενο θωρακα πιστεως κα αγαπης). First aorist (ingressive) middle participle of ενδυω. The same figure of breastplate in Eph 6:14, only there "of righteousness." The idea of watchfulness brings the figure of a sentry on guard and armed to Paul's mind as in Ro 13:12 "the weapons of light." The word θωραξ (breastplate) is common in the LXX.

For a helmet, the hope of salvation (περικεφαλαιαν ελπιδα σωτηριας). Same figure in Eph 6:17 and both like Isa 59:17. Late word meaning around (περ) the head (κεφαλη) and in Polybius, LXX, and in the papyri. Σωτηριας is objective genitive.