"I remained in Medina for seven months with the Prophet, peace be upon him, and I heard the Prophet, when the dawn emerged, come to the door of Ali and Fatima and say: 'Prayer!' [repeating it] three times: 'Allah only intends to remove from you the rijs (impurity), O people of the [Prophet's] house, and to purify you with a complete purification' (33:33)."

Surat al-Ahzab (Verse 35)