From Sahih Muslim (Hadith 4269):
Abu Musa al-Ash'ari reported:We came to Allah's Messenger (ﷺ) requesting him to provide us with riding camels. He (the Holy Prophet) said: There is nothing with me with which I should equip you. By Allah, I would not provide you with (riding camels). Then Allah's Messenger (ﷺ) sent to us three camels with spotted bumps. We said: We came to Allah's Messenger (ﷺ) asking him to equip us with riding animals. He took an oath that he could not equip us. We came to him and informed him. He said: By Allah, I do not take an oath, but when I find the other thing better than that, I do that which is better
Reference: Muslim 4269