Sayyiduna Ma'bad al-Qurashi (may Allah be pleased with him) said: The Prophet (peace and blessings be upon him) was at Qudayd when a man came to him. The Prophet (peace and blessings be upon him) said to him: "Have you eaten anything today, the day of Ashura?" He said: No, except that I drank some water. He (peace and blessings be upon him) said: "Then do not eat anything until the sun sets, and order those behind you to fast this day."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17934