Sahih Bukhari Volume 8, Book 78, Hadith Number 669.

Narated By Abu Musa : My companions sent me to the Prophet to ask him for some mounts. He said, “By Allah! I will not mount you on anything!” When I met him, he was in an angry mood, but when I met him (again), he said, “Tell your companions that Allah or Allah’s Apostle will provide you with mounts.”