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 c

Ibn 'Umar (Allah be pleased with them) reported that the Messenger of Allah (ﷺ) pronounced Talbiya in Dhu'l-Hulaifa as he put his feet in the stirrup and his camel stood up and proceeded.

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، - رضى الله عنهما - قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا وَضَعَ رِجْلَهُ فِي الْغَرْزِ وَانْبَعَثَتْ بِهِ رَاحِلَتُهُ قَائِمَةً أَهَلَّ مِنْ ذِي الْحُلَيْفَةِ ‏.‏
Reference : Sahih Muslim 1187c
In-book reference : Book 15, Hadith 30
USC-MSA web (English) reference : Book 7, Hadith 2676
  (deprecated numbering scheme)