Hadith 418:1
Abdullah ibn Ahmad said: Muhammad ibn Abi Bakr al-Muqaddami narrated to me, he said: Abu Ma’shar al-Bara’ narrated to us, he said: Ibn Harmalah narrated to us, from Yahya ibn Hind ibn Harithah, from his father—and he was among the companions of al-Hudaybiyah, and his brother whom the Messenger of Allah (peace be upon him) sent to command his people to fast the day of Ashura was Asma’ ibn Harithah: That the Messenger of Allah (peace be upon him) sent him and said: "Command your people to fast this day." He said: "What if I find that they have already eaten?" He said: "Then let them complete the rest of their day."
قال عبد الله بن أحمد: حدثني محمد بن أبي بكر المقدمي، قال: حدثنا أبو معشر البراء، قال: حدثنا ابن حرملة، عن يحيى بن هند بن حارثة، عن أبيه - وكان من أصحاب الحديبية، وأخوه الذي بعثه رسول الله صلى الله عليه وسلم يأمر قومه بصيام يوم عاشوراء وهو أسماء بن حارثة: أن رسول الله صلى الله عليه وسلم بعثه، فقال: " مر قومك فليصوموا هذا اليوم " قال: أرأيت إن وجدتهم قد طعموا؟ قال " فليتموا آخر يومهم "