Musnad Ahmad 627:14

Bahz narrated to us, Shu'bah narrated to us, 'Abd al-'Aziz ibn Rufay' informed me, he said: I heard Tamim ibn Tarafah al-Ta'i narrating from 'Adi ibn Hatim, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever swears an oath, then sees something else to be better than it, let him come to that which is better, and let him leave his oath."