Musannaf Ibn Abi Shayba 27:634

Shadhan narrated to us, he said: Hammad bin Salamah narrated to us, from Ali bin Zaid, from Anas bin Malik, that the Prophet (peace and blessings of Allah be upon him) used to pass by the house of Fatimah for six months when he went out for the dawn prayer. He would say: "The prayer, O people of the house! 'Allah only intends to remove from you the impurity, O people of the [Prophet's] household, and to purify you with [extensive] purification.'"