It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that once on the day of Ashura, the Noble Prophet (peace and blessings be upon him) observed a fast and said to the companions (may Allah be pleased with them): Whoever among you has kept a fast should complete his fast, and whoever has eaten something in the morning should not eat or drink for the rest of the day.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 8716
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لضعف عبدالصمد، وجهالة أبيه