Sahih al-Bukhari 7555

Narrated Zahdam:There were good relations and brotherhood between this tribe of Jurm and the Ash`ariyyin. Once, while we were sitting with Abu Musa Al-Ash`ari, there was brought to him a meal which contained chicken meat, and there was sitting beside him, a man from the tribe of Bani Taimul-lah who looked like one of the Mawali. Abu Musa invited the man to eat but the man said, "I have seen chicken eating some dirty things, and I have taken an oath not to eat chicken." Abu Musa said to him, "Come along, let me tell you something in this regard. Once I went to the Prophet (ﷺ) with a few men from Ash`ariyyin and we asked him for mounts. The Prophet (ﷺ) said, By Allah, I will not mount you on anything; besides I do not have anything to mount you on.' Then a few camels from the war booty were brought to the Prophet, and he asked about us, saying, 'Where are the group of Ash`ariyyin?' So he ordered for five fat camels to be given to us and then we set out. We said, 'What have we done? Allah's Messenger (ﷺ) took an oath that he would not give us anything to ride and that he had nothing for us to ride, yet he provided us with mounts. We made Allah's Messenger (ﷺ) forget his oath! By Allah, we will never be successful.' So we returned to him and reminded him of his oath. He said, 'I have not provided you with the mount, but Allah has done so. By Allah, I may take an oath to do something, but on finding something else which is better, I do that which is better and make the expiation for my oath.' "