that the people were in doubt whether the Prophet ﷺ was fasting on the Day of ʿArafat or not, so a (wooden) drinking vessel full of milk was sent to him, and he drank it.  

عَنْ أُمِّ الْفَضْلِ أَنَّهُمْ شَكُّوا فِي صَوْمِ النَّبِيِّ ﷺ يَوْمَ عَرَفَةَ فَبُعِثَ إِلَيْهِ بِقَدَحٍ مِنْ لَبَنٍ فَشَرِبَهُ