Sahih al-Bukhari 4906

It is related from 'Abdullah ibn al-Fadl that he heard Anas ibn Malik say, "I was grieved about those who were killed at the Battle of al-Harra*. Zayd ibn Arqam, who had heard of my great sorrow, wrote to me, mentioning that he heard the Messenger of Allah, may Allah bless him and grant him peace, say, 'O Allah, forgive the Ansar and the sons of the Ansar!'" Ibn al-Fadl was uncertain about whether he also said, "The sons of the sons of the Ansar." Some of those who were with Anas, asked himand he said, "He is the one about whom the Messenger of Allah, may Allah bless him and grant him peace, said, 'This is the one whose hearing Allah confirmed.'" [* al-Harra was a battle between the forces of Yazid ibn Mu'awiya and the people of Makka which took place outside of Madina in 63/683. The Madinans were supporting the claim of 'Abdullah ibn az-Zubayr.]