Guarding One’s Words Grants Strength to Battle the Yeitzer Hara
Rashi explains the words “like the opening of a coat of armor” by saying: “We learn from here that their coats of armor had the opening folded inward.”
Rav Henoch of Alesk zy”a (Siddur Lev Sameach) sees this as a hint that our “coat of armor” – our protection in our battle against the yeitzer hara – is the strength we derive from guarding our speech. We receive this strength when we “fold our mouth inward” and refrain from speaking negatively about others.