Abdullah bin Shihab al-Khawlani said: I was a guest of Sayyidah Aishah (may Allah be pleased with her). I became junub, so I dipped my clothes in water. A slave girl of Sayyidah Aishah (may Allah be pleased with her) saw me and informed her. Sayyidah Aishah (may Allah be pleased with her) sent her to me, then said: "What made you do that with your clothes?" I said: "I saw what a sleeper sees." Sayyidah Aishah (may Allah be pleased with her) asked: "Did you see any trace?" I said: "No." She said: "Had you seen something, you would wash it. I remember that I used to scrape dried semen off the clothes of the Prophet (peace and blessings be upon him) with my fingernails."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4171