Ishaq bin Ibrahim bin Muhammad إسحاق بن إبراهيم بن محمد · The Book of Oaths and Vows

"The Messenger of Allah said: 'Whoever swears an oath, then sees something better than it, let him do that which is better and offer expiation for his oath.'"

The Messenger of Allah said: "There is no vow at a moment of anger and its expiation is the expiation for an oath."