Some scholars say that sperm is impure, but apparently it is pure, for it is only recommended to wash it off if it is still wet, and to scratch it off if it is dry. Said ‘Aishah, “I used to scratch the sperm off the Messenger of Allah’s clothes if it was dry, and wash it off if it was still wet.” (This is related by ad-Daraqutni, Abu ‘Awanah and al-Bazzar). It is also related that Ibn ‘Abbas said, “I asked the Messenger of Allah about sperm on clothes. He said, ‘It is the same as mucus and spittle. It is sufficient to rub the area with a rag or cloth.”‘
The hadith was related by ad-Daraqutni, al-Baihaqi and atTahawi. There is a difference in the narration over whether it should be in marfu’or mauqoof form.