كتاب الحج
15  
The Book of Pilgrimage
(65)
Chapter: It is permissible to ride the sacrificial animal if necessary
(65)
باب جَوَازِ رُكُوبِ الْبَدَنَةِ الْمُهْدَاةِ لِمَنِ احْتَاجَ إِلَيْهَا ‏‏
Sahih Muslim 1322 b

This hadith has been narrated by A'raj with the same chain of transmitters (and the words are):

" Whereas the person was driving a sacrificial camel which was garlanded."
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا الْمُغِيرَةُ بْنُ عَبْدِ الرَّحْمَنِ الْحِزَامِيُّ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، بِهَذَا الإِسْنَادِ وَقَالَ بَيْنَمَا رَجُلٌ يَسُوقُ بَدَنَةً مُقَلَّدَةً ‏.‏
Reference : Sahih Muslim 1322b
In-book reference : Book 15, Hadith 413
USC-MSA web (English) reference : Book 7, Hadith 3047
  (deprecated numbering scheme)