Musnad Ahmad 627:21

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, Simak narrated to us, from Tamim ibn Tarafah, who said: I heard ‘Adi ibn Hatim, and a man came to him asking him for one hundred dirhams. He said: "You ask me for one hundred dirhams, and I am the son of Hatim? By Allah, I will not give you." Then he said: "Were it not that I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'Whoever swears an oath, then sees that something else is better than it, let him do that which is better.'"