Musannaf Ibn Abi Shayba 1:913

Abu Bakr narrated to us, he said: 'Abdah bin Sulayman narrated to us, from 'Amr bin Maymun, he said: I asked Sulayman bin Yasar about a garment that semen touches: "Should he wash it, or wash the whole thing?" Sulayman said: 'Aishah said: "The Prophet, peace and blessings of Allah be upon him, would have it touch his garment, so he would wash it from his garment, then he would go out in his garment to the prayer, and I would see the trace of the washing on it."