Sahih Muslim Book - 13, Hadith - 2632

حَدَّثَنَا يَحْيَى بْنُ يَحْيَى قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ أَبِى النَّضْرِ عَنْ عُمَيْرٍ مَوْلَى عَبْدِ اللَّهِ بْنِ عَبَّاسٍ عَنْ أُمِّ الْفَضْلِ بِنْتِ الْحَارِثِ أَنَّ نَاسًا تَمَارَوْا عِنْدَهَا يَوْمَ عَرَفَةَ فِى 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.

It was narrated from Abdullah bin Abbas, from umm al-Fadl bint Al-Harth:”Some people argued in her presence on the day of Arafah about the fasting of the Messenger of Allah (SAW). Some of them said that he was fasting, and some of them said that he was not fasting. I (Umm Al-Fadl) sent a vessel of milk while he was sitting on his camel (in the Mawaqif or place of standing at Arafah), and he drank it.”