Go out from him; not through weakness of the parts, as that Leviticus 15:3; but in his sleep, which is called nightly pollution, which, though involuntary, might arise from some lustful dream or imagination. But if it was voluntary, and by a man's own procurement when awake, it was esteemed abominable, and a degree of murder. See Genesis 38:9.
Related Commentaries of Leviticus 15:16
Leviticus 15:16
16 And if any man's seed of copulation go out from him, then he shall wash all his flesh in water, and be unclean until the even.