Ata bin Abi Rabah (may Allah have mercy on him) says that once Abdullah bin Abbas (may Allah be pleased with them both) invited his brother Fadl (may Allah be pleased with him) to eat on the day of Arafah. He replied that he was fasting. Ibn Abbas (may Allah be pleased with them both) said: Do not fast on this day (while in the state of Ihram), because milk was milked and presented to the Prophet (peace and blessings of Allah be upon him) in a vessel on this day, and the Prophet (peace and blessings of Allah be upon him) drank it, and people follow your example (if they see you fasting, they might start considering it important).