יֹ֭שְׁבֵי חֹ֣שֶׁךְ וְצַלְמָ֑וֶת אֲסִירֵ֖י עֳנִ֣י וּבַרְזֶֽל׃
Such as sat in darkness and in the shadow of death, Being bound in affliction and iron—
Rashi on Psalms
Those who sit in darkness and the shadow of death Also those imprisoned in a dungeon are required to give thanks when they emerge from their prison.