It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that on the day of Arafah he invited Sayyiduna al-Fadl bin Abbas (may Allah be pleased with them both) to a meal, and he said: "I am fasting." At this Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: "Do not fast, for on this day (of Arafah) a vessel of milk was brought to the Prophet (peace and blessings be upon him) and he (peace and blessings be upon him) drank it; and indeed the people follow your example."
Hadith Referenceمسند أبي يعلى الموصلي / أول مسند ابن عباس / 2744
Hadith Takhrij«قال سعيد بن محمد السناري: صحيح» «أخرجه سنن الترمذي برقم: 750، وأخرجه مسند أحمد برقم: 2940، وأخرجه المعجم الأوسط للطبراني برقم: 9182، مسند ابویعلیٰ ترقیم الاثری: 2736»