It is narrated from Sayyidah Aishah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) said: "A ritual bath is taken for four things: for major impurity (janabah), on Friday, after washing a dead person, and after cupping."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1429