Here "bare" does not necessarily mean naked, but to wear minimal covering such as undergarments. Alternate translation: "take off you fine clothes and make yourself unclothed" or "take off your fancy clothes" (See: [[rc://en/ta/man/translate/figs-explicit]])
This is an act of grieving or mourning. Alternate translation: "put sackcloth around waists as you grieve" (See: [[rc://en/ta/man/translate/translate-symaction]])