Leviticus 15:16-18

16“ ‘When a man has an emission of semen, he must bathe his whole body with water, and he will be unclean till evening. 17Any clothing or leather that has semen on it must be washed with water, and it will be unclean till evening.

18When a man has sexual relations with a woman and there is an emission of semen, both of them must bathe with water, and they will be unclean till evening.