Musannaf Ibn Abi Shayba 27:440

Abu Mu'awiyah narrated to us, from Musa ibn Muslim, from Abd al-Rahman ibn Sabit, from Sa'd, who said: Mu'awiyah arrived during one of his pilgrimages, and Sa'd came to him. They mentioned Ali, and Mu'awiyah spoke ill of him. Sa'd became angry and said: "Do you say this about a man of whom I heard the Messenger of Allah (peace and blessings of Allah be upon him) say three qualities? That I should have one of them is more beloved to me than the world and what is in it." "I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'Whoever I am his master (mawla), then Ali is his master (mawla).' And I heard the Prophet (peace and blessings of Allah be upon him) say: 'You are to me in the position of Aaron to Moses, except that there is no prophet after me.' And I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'I will certainly give the banner to a man who loves Allah and His Messenger.'"