Sahih Bukhari Volume 2, Book 25, Hadith 1555

حَدَّثَنَا سُلَيْمَانُ بْنُ دَاوُدَ أَبُو الرَّبِيعِ، حَدَّثَنَا فُلَيْحٌ، عَنْ نَافِعٍ، قَالَ كَانَ ابْنُ عُمَرَ ـ رضى الله عنهما ـ إِذَا أَرَادَ الْخُرُوجَ إِلَى مَكَّةَ ادَّهَنَ بِدُهْنٍ لَيْسَ لَهُ رَائِحَةٌ طَيِّبَةٌ، ثُمَّ يَأْتِي مَسْجِدَ الْحُلَيْفَةِ فَيُصَلِّي ثُمَّ يَرْكَبُ، وَإِذَا اسْتَوَتْ بِهِ رَاحِلَتُهُ قَائِمَةً أَحْرَمَ، ثُمَّ قَالَ هَكَذَا رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم يَفْعَلُ

Narrated By Nafi' : 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.