Sahih al-Bukhari — One-fifth of Booty to the Cause of Allah (Khumus) — Hadith No: 3133
Translation
Narrated Zahdam:Once we were in the house of Abu Musa who presented a meal containing cooked chicken. A man from the tribe of Bani Taim Allah with red complexion as if he were from the Byzantine war prisoners, was present. Abu Musa invited him to share the meal but he (apologised) saying. "I saw chickens eating dirty things and so I have had a strong aversion to eating them, and have taken an oath that I will not eat chickens." Abu Musa said, "Come along, I will tell you about this matter (i.e. how to cancel one's oath). I went to the Prophet (ﷺ) in the company of a group of Al-Ashariyin, asked him to provide us with means of conveyance. He said, 'By Allah, I will not provide you with any means of conveyance and I have nothing to make you ride on.' Then some camels as booty were brought to Allah's Messenger (ﷺ) and he asked for us saying. 'Where are the group of Al-Ash`ariyun?' Then he ordered that we should be given five camels with white humps. When we set out we said, 'What have we done? We will never be blessed (with what we have been given).' So, we returned to the Prophet (ﷺ) and said, 'We asked you to provide us with means of conveyance, but you took an oath that you would not provide us with any means of conveyance. Did you forget (your oath when you gave us the camels)? He replied. 'I have not provided you with means of conveyance, but Allah has provided you with it, and by Allah, Allah willing, if ever I take an oath to do something, and later on I find that it is more beneficial to do something different, I will do the thing which is better, and give expiation for my oath