Musnad Ahmad Hadith 1607

I heard the Messenger of Allah (ﷺ) say to ["Ali], when he left him in charge [of Madinah] during one of his campaigns. ‘Ali said: O Messenger of Allah, are you leaving me behind with the women and children? He said: "Does it not please you to be to me as Haroon was to Moosa, except there will be no Prophet (ﷺ) after me?" And I heard him say on the day of Khaibar: "I shall certainly give the banner to a man who loves Allah and His Messenger, and Allah and His Messenger love him." We all hoped for it, but he said: "Call "Ali for me.” He was brought, and he had a sore eye. [The Prophet (ﷺ) ] spat in his eye and gave the banner to him, and Allah granted victory at his hands. And when this verse was revealed: "let us call our sons and your sons" (Al-"Imran 3:61], the Messenger of Allah (ﷺ) called "Ali, Fatimah, Hasan and Husain, (رضي الله عنه) and said: "O Allah, these are my family.”