Musnad Ahmad 774:12

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from 'Amr ibn Murrah, who said: I heard 'Abdullah ibn 'Amr narrating from 'Adi ibn Hatim, that a man came to him asking him. He said: So he asked him about something he considered insignificant, so he swore an oath. Then he said: "Were it not that I heard the Messenger of Allah, may Allah bless him and grant him peace, say: 'Whoever swears an oath, then sees something else to be better than it, let him do that which is better, and let him offer expiation for his oath.'" Abu 'Abd al-Rahman said: "This is a hadith I have never heard from anyone at all except from my father."