Sahih Bukhari, Chapter: Pilgrimage (Hajj)

Whenever Ibn 'Umar intended to go to Mecca he used to oil himself with a sort of oil that had no pleasant smell, then he would go to the Mosque of Al-Hulaita and offer the prayer, and then ride. When he mounted well on his Mount and the Mount stood up straight, he would proclaim the intention of assuming Ihram, and he used to say that he had seen the Prophet doing the same.