Albert Barnes Commentary Leviticus 22:4

"What man soever of the seed of Aaron is a leper, or hath an issue; he shall not eat of the holy things, until he be clean. And whoso toucheth anything that is unclean by the dead, or a man whose seed goeth from him;" — Leviticus 22:4 (ASV)

See Leviticus 15:13-16.