It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him), on the day of Ashura, sent a message to a village that was at a distance of four or two farsakhs: "Whoever has not eaten, let him complete his fast; and whoever has eaten, let him not eat for the rest of the day."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11754