Sayyiduna Abd al-Rahman bin Samurah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "O Abd al-Rahman bin Samurah! When you swear an oath about something, and then there is something better than it, do that and give the expiation for your oath."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19946