Abu Ammar (may Allah have mercy on him) said: I was sitting with Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) when people mentioned Sayyiduna Ali (may Allah be pleased with him) and reviled him. When those people got up and left, Sayyiduna Wathilah (may Allah be pleased with him) said (to me): Sit, and I will tell you about this person whom they have reviled: One day I was with the Messenger of Allah (peace and blessings be upon him) when Sayyiduna Ali, Sayyidah Fatimah, Sayyiduna Hasan and Sayyiduna Husayn (may Allah be pleased with them) came, and he (peace and blessings be upon him) cast his cloak over them, then said: "O Allah, these are my household. O Allah, remove impurity from them and purify them thoroughly." I said: O Messenger of Allah, and I? He said: "You too." Sayyiduna Wathilah (may Allah be pleased with him) said: By Allah, this is the deed I rely upon most.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2656