Musnad Ahmad 567:0

Narrated to us by Yahya ibn Sa’id, from Sufyan, who said: Narrated to us by Habib ibn Abi Thabit, from a man from Banu al-Dil, who said: I was with the Messenger of Allah (ﷺ) when a man came to him and said: "O Messenger of Allah, what is the most virtuous of deeds?" He replied: "Good character." Then the man came to him from his right side and said: "O Messenger of Allah, what is the most virtuous of deeds?" He replied: "Good character." Then the man came to him from his left side and said: "O Messenger of Allah, what is the most virtuous of deeds?" He replied: "Good character." Then the man came to him from behind him and said: "O Messenger of Allah, what is the most virtuous of deeds?" The Messenger of Allah (ﷺ) turned to him and said: "Why do you not understand? Good character is that you do not become angry."