He was among the Companions of Hudaybiyyah. His brother, whom the Messenger of Allah ﷺ sent to command his people to fast the day of Ashura, was Asma bin Haritha. The Messenger of Allah ﷺ sent him and said, "Order your people to fast this day."He asked, "What if I find that they have already eaten?"He replied, "Then let them complete the rest of their day."
حدثنا عبد الله قال حدثني محمد بن أبي بكر المقدمي قال حدثنا أبو معشر البراء قال حدثنا ابن حرملة
وكان من أصحاب الحديبية وأخوه الذي بعثه رسول الله ﷺ يأمر قومه بصيام يوم عاشوراء وهو أسماء بن حارثة أن رسول الله ﷺ بعثه فقال مر قومك فليصوموا هذا اليوم قال أرأيت إن وجدتهم قد طعموا قال فليتموا بقية يومهم
Its isnad is sahih. Abu Mashar Bara is Abdul-Rahman bin Harmala bin Sana Aslami. As for Yahya bin Hind bin Haritha, there is disagreement about whether he was a companion. Ibn Hibban mentioned him among the trustworthy successors in 5/525, and also mentioned him among the companions in 3/447. The hadith has appeared previously at 16478, and here it is among the additional narrations, where it is from Salama bin Akwa.