It is narrated from Zahdam al-Jarmi (may Allah have mercy on him) (the narrator said: I remember al-Qasim's narration better) that he said: We were with Abu Musa (may Allah be pleased with him). He called for a dining cloth, and on it was chicken meat. A red-complexioned man from the tribe of Banu Taym Allah came in. Abu Musa (may Allah be pleased with him) said: "Come." He made an excuse, so Abu Musa (may Allah be pleased with him) said: I saw the Prophet (peace and blessings be upon him); he (peace and blessings be upon him) used to eat it, or eat from it. He said: By Allah, I too saw it eating certain things, because of which I swore that I would not eat its meat. Abu Musa (may Allah be pleased with him) said: Come, I will tell you: the Messenger of Allah (peace and blessings be upon him) said: "If I swear an oath about something and something else is better than it, I do that and give the expiation for my oath. Go, Allah has given you mounts."
(b) Hammad bin Zayd and others say that he (peace and blessings be upon him) said: "I do the better thing and end my oath."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19952