Sahih Muslim | Book 2 | Hadith Number 570

Narrated by 'Amr b. Maimun
'Amr b. Maimun said: I asked Sulaiman b. Yasir whether the semen that gets on to the garment of a person should be washed or not. He replied: 'Aisha told me: The Messenger of Allah (may peace be upon him) washed the semen, and then went out for prayer in that very garment and I saw the mark of washing on it.