Sahih Bukhari Volume 5, Book 64, Hadith 4279

حَدَّثَنِي عَيَّاشُ بْنُ الْوَلِيدِ، حَدَّثَنَا عَبْدُ الأَعْلَى، حَدَّثَنَا خَالِدٌ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ خَرَجَ النَّبِيُّ صلى الله عليه وسلم فِي رَمَضَانَ إِلَى حُنَيْنٍ، وَالنَّاسُ مُخْتَلِفُونَ فَصَائِمٌ وَمُفْطِرٌ، فَلَمَّا اسْتَوَى عَلَى رَاحِلَتِهِ دَعَا بِإِنَاءٍ مِنْ لَبَنٍ أَوْ مَاءٍ، فَوَضَعَهُ عَلَى رَاحَتِهِ أَوْ عَلَى رَاحِلَتِهِ، ثُمَّ نَظَرَ إِلَى النَّاسِ فَقَالَ الْمُفْطِرُونَ لِلصُّوَّامِ أَفْطِرُوا‏

Narrated By Ibn Abbas : Allah's Apostle set out towards Hunain in the month of Ramadan and some of the people were fasting while some others were not fasting, and when the Prophet mounted his she-camel, he asked for a tumbler of milk or water and put it on the palm of his hand or on his she-camel and then the people looked at him; and those who were not fasting told those who were fasting, to break their fast (i.e. as the Prophet had done so).