It is recommended for the person performing Hajj in 'Arafat not to fast on the day of 'Arafah.

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.

حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ أَبِي النَّضْرِ، عَنْ عُمَيْرٍ، مَوْلَى عَبْدِ اللَّهِ بْنِ عَبَّاسٍ عَنْ أُمِّ الْفَضْلِ بِنْتِ الْحَارِثِ، أَنَّ نَاسًا، تَمَارَوْا عِنْدَهَا يَوْمَ عَرَفَةَ فِي صِيَامِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ بَعْضُهُمْ هُوَ صَائِمٌ وَقَالَ بَعْضُهُمْ لَيْسَ بِصَائِمٍ ‏.‏ فَأَرْسَلْتُ إِلَيْهِ بِقَدَحِ لَبَنٍ وَهُوَ وَاقِفٌ عَلَى بَعِيرِهِ بِعَرَفَةَ فَشَرِبَهُ ‏.‏

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.

حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، وَابْنُ أَبِي عُمَرَ، عَنْ سُفْيَانَ، عَنْ أَبِي النَّضْرِ، بِهَذَا الإِسْنَادِ ‏.‏ وَلَمْ يَذْكُرْ وَهُوَ وَاقِفٌ عَلَى بَعِيرِهِ ‏.‏ وَقَالَ عَنْ عُمَيْرٍ مَوْلَى أُمِّ الْفَضْلِ ‏.‏

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.

حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، عَنْ سُفْيَانَ، عَنْ سَالِمٍ أَبِي، النَّضْرِ بِهَذَا الإِسْنَادِ نَحْوَ حَدِيثِ ابْنِ عُيَيْنَةَ وَقَالَ عَنْ عُمَيْرٍ، مَوْلَى أُمِّ الْفَضْلِ ‏.‏

Umm al-Fadl (Allah be pleased with her) is reported to have said that some people among the Companions of the Messenger of Allah (ﷺ) were in doubt about fasting on the day of 'Arafa and we were with him on that day. I (Umm al-Fadl) sent him a cup of milk and he was halting at 'Arafa, and he drank that.

وَحَدَّثَنِي هَارُونُ بْنُ سَعِيدٍ الأَيْلِيُّ، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي عَمْرٌو، أَنَّ أَبَا النَّضْرِ، حَدَّثَهُ أَنَّ عُمَيْرًا مَوْلَى ابْنِ عَبَّاسٍ - رضى الله عنهما - حَدَّثَهُ أَنَّهُ، سَمِعَ أُمَّ الْفَضْلِ، - رضى الله عنها - تَقُولُ شَكَّ نَاسٌ مِنْ أَصْحَابِ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي صِيَامِ يَوْمِ عَرَفَةَ وَنَحْنُ بِهَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَأَرْسَلْتُ إِلَيْهِ بِقَعْبٍ فِيهِ لَبَنٌ وَهُوَ بِعَرَفَةَ فَشَرِبَهُ ‏.‏

Kuraib, the freed slave of Ibn 'Abbas (Allah be pleased with him), reported from Maimuna, the wife of the Messenger of Allah (ﷺ), that people had doubt about the fasting of Allah's Messenger (ﷺ) on the day of 'Arafa. Maimuna sent him a cup of milk and he was halting at a place and he drank it and the people were seeing him.

وَحَدَّثَنِي هَارُونُ بْنُ سَعِيدٍ الأَيْلِيُّ، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي عَمْرٌو، عَنْ بُكَيْرِ بْنِ، الأَشَجِّ عَنْ كُرَيْبٍ، مَوْلَى ابْنِ عَبَّاسٍ - رضى الله عنهما - عَنْ مَيْمُونَةَ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَنَّهَا قَالَتْ إِنَّ النَّاسَ شَكُّوا فِي صِيَامِ رَسُولِ اللَّهِ صلى الله عليه وسلم يَوْمَ عَرَفَةَ فَأَرْسَلَتْ إِلَيْهِ مَيْمُونَةُ بِحِلاَبِ اللَّبَنِ وَهُوَ وَاقِفٌ فِي الْمَوْقِفِ فَشَرِبَ مِنْهُ وَالنَّاسُ يَنْظُرُونَ إِلَيْهِ ‏.‏