Umm Habibah bint Kaysan (may Allah have mercy on her) narrates from Sayyidah Umm Salamah (may Allah be pleased with her); she said: This verse was revealed: "Allah only intends to remove impurity from you, O members of the household" [Surah al-Ahzab: 33], while I was in my house. The Messenger of Allah (peace and blessings be upon him) called Sayyiduna al-Hasan and Sayyiduna al-Husayn (may Allah be pleased with them both), seated one of them on his right thigh and the other on his left thigh, and Sayyidah Fatimah (may Allah be pleased with her) cast a cloak over them. Then, when this verse was revealed: "Allah only intends to remove impurity from you, O members of the household" [Surah al-Ahzab: 33], I said: Am I also with you, O Messenger of Allah? He (peace and blessings be upon him) said: "Yes, you too are with us."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20141