Sahih Muslim Book 15, Hadith Number 4061.

Chapter : It is excellent to break the vow if one finds it better doing that which is against this vow one should expiate it.

Tamim b. Tarafa reported: I heard ‘Adi b. Hatim say that a person asked that and then narrated (the hadith) like one (mentioned above), but he made this addition: “Here are four hundred (dirhams) for you out of my gift.”