Sahih Muslim
The Book of Purification (Kitab Al-Taharah)
Book Number: 002 / Hadith Number: 568
Qutaiba b. Sa'id, Ishaq b. Ibrahim, Ibn Abi 'Aruba, Abu Ma'shar, Abu Bakr b. Abu Shaiba, Mansur and Mughira have all transmitted from Ibrahim, who transmitted it on the authority of A'isha's narration pertaining to the scraping off of the (drop) of semen from the garment of the Messenger of Allah (may peace be upon him) like the hadith of Khalid on the authority of Abu Ma'shar.