en_tn_lite_do_not_use/deu/23/10.md

any man who is unclean because of what happened to him at night

This is a polite way of saying that he had an emission of semen. Alternate translation: "any man who is unclean because he had an emission of semen while he was asleep" (See: rc://en/ta/man/jit/figs-euphemism)