Mishnà su Levitico 15:18

If a non-Jewish woman discharged semen from an Israelite, it is unclean. If an Israelite woman discharged semen from a non-Jewish man, it is clean. If a woman had intercourse and then went down and immersed herself but did not sweep out the house, it is as though she had not immersed herself. If a man who had a seminal emission immersed himself but did not first pass urine, he again becomes unclean when he passes urine. Rabbi Yose says: if he was sick or old he is unclean, but if he was young and healthy he remains clean.