Sahih Bukhari
Ablutions (Wudu)
Volume: 001 / Book Number: 004 / Hadith Number: 231
Narrated Sulaiman bin Yasar:
I asked 'Aisha about the clothes soiled with semen. She replied, "I used to wash it off the clothes of Allah's Apostle and he would go for the prayer while water spots were still visible. "