It is narrated from Sayyidah Aishah (may Allah be pleased with her) that a man asked: If someone has intercourse with his wife and then becomes slack, is ghusl required of him? And Aishah (may Allah be pleased with her) was sitting there, so the Messenger of Allah (peace and blessings be upon him) said: "I and this one (Aishah, may Allah be pleased with her) do that, and then we perform ghusl."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 768