It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that Sayyiduna Abu Musa (may Allah be pleased with him) came to the Messenger of Allah (peace and blessings be upon him) asking him for a mount. (Then the narrator mentioned the full hadith.)
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15574