كتاب الحج
15  
The Book of Pilgrimage
(5)
Chapter: Clarifying that it is better to enter Ihram when a person's mount sets off with him, heading towards Makkah, not straight after the two rak'ah
(5)
باب الإِهْلاَلِ مِنْ حَيْثُ تَنْبَعِثُ الرَّاحِلَةُ ‏
Sahih Muslim 1187 e

'Abdullah b. 'Umar reported:

I saw the Messenger of Allah (ﷺ) riding on his camel at Dhu'l-Hulaifa and pronouncing Talbiya as it stood up with him.
وَحَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، أَنَّأَخْبَرَهُ أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ - رضى الله عنهما - قَالَ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم رَكِبَ رَاحِلَتَهُ بِذِي الْحُلَيْفَةِ ثُمَّ يُهِلُّ حِينَ تَسْتَوِي بِهِ قَائِمَةً ‏.
Reference : Sahih Muslim 1187e
In-book reference : Book 15, Hadith 32
USC-MSA web (English) reference : Book 7, Hadith 2678
  (deprecated numbering scheme)