It is narrated from Sayyiduna Khabbab (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said on the day of Ashura: "O people! Whoever among you has eaten, let him not eat for the rest of the day, and whoever has intended to fast, let him fast it."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3677