Abu Jamilah said: When Sayyiduna Ali (may Allah be pleased with him) was martyred, Sayyiduna al-Hasan bin Ali (may Allah be pleased with him) was made caliph. Once, while he was leading the people in prayer, a man leapt upon him and stabbed him with a dagger in his thigh (hip), and he was ill from it for several months. Then he stood on the pulpit to deliver a sermon and said: "O people of Iraq! Fear Allah regarding us, for we are your rulers and your guests, and we are the very household (Ahl al-Bayt) about whom Allah, the Mighty and Majestic, said: 'Allah only intends to remove from you all impurity, O people of the household, and to purify you thoroughly' [Surah al-Ahzab: 33]." He kept speaking that day until there was no one to be seen in the mosque who was not weeping.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2748