This hadith has been narrated on the authority of Abu Nadr with the same chain of transmitters, but he did not mention that he was mounting (riding on) his camel.
Sahih Muslim Book 13, Hadith 139
← Previous Hadith Umm al-Fadl bint- al-Harith reported that some people argued about the fasting of the Messenger of Allah (ﷺ) on the day of 'Arafa. Some of them said that he had been fasting, whereas the others said that he had not been fasting. I sent a cup of milk to him while he was riding his camel at 'Arafa, and he drank it.

Sahih Muslim Book 13, Hadith 138 Next Hadith → This hadith has been narrated by Abu Nadr on the authority of Umair, the freed slave of Umm al-Fadl, through the same chain of transmitters.

Sahih Muslim Book 13, Hadith 140