It is narrated from the Mother of the Believers, Sayyidah Aishah (may Allah be pleased with her) that she said: "The Messenger of Allah (peace and blessings be upon him) would see traces of semen on the wrap of one of us, then he would scrape it off."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Imam al-Zuhri (may Allah have mercy on him) except Ja'far bin Burqan (may Allah have mercy on him)."