en_tn/psa/069/011.md

I made sackcloth my clothing

Wearing rough, cheap clothing was a symbol of mourning over sin. (See: rc://en/ta/man/jit/translate-symaction)

I became a byword to them

The writer speak of himself as if he was the sad or foolish person spoken; one who is spoken of in a rhyme or proverb; the taunting was intended to bring shame to him. Alternate translation: "I became the example of a sad person spoken of in their proverbs" or "they laugh at me" (See: rc://en/ta/man/jit/figs-metaphor)