Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) set out for Hunayn in Ramadan, and the people differed: some were fasting and some were not fasting. When he (peace and blessings be upon him) sat upright on his mount, he called for a vessel of milk or water and drank it. The narrator said: Then he (peace and blessings be upon him) placed it on his mount. Then the people saw (him), and those who were not fasting said to those who were fasting: "Break your fast."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11915