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Ibn Abbas (Allah be pleased with him) reported that Allah's Messenger (may peace be upon, him) came back from 'Arafa and Usama (Allah be pleased with him) was seated behind him. Usama said that he (the Holy Prophet) continued the journey in this very state until he came to Muzdalifa.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا يَزِيدُ بْنُ هَارُونَ، أَخْبَرَنَا عَبْدُ الْمَلِكِ بْنُ أَبِي سُلَيْمَانَ، عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَفَاضَ مِنْ عَرَفَةَ وَأُسَامَةُ رِدْفُهُ قَالَ أُسَامَةُ فَمَازَالَ يَسِيرُ عَلَى هَيْئَتِهِ حَتَّى أَتَى جَمْعًا .
sunnah.com