The Messenger of Allah ﷺ allotted a man and his horse three shares, one share for the man and two shares for his horse.
حدثنا أحمد بن حنبل حدثنا أبو معاوية حدثنا عبيد الله عن نافع
أن رسول الله ﷺ أسهم لرجل ولفرسه ثلاثة أسهم سهما له وسهمين لفرسه
Its isnad is sahih. Bukhari narrated it in the Book of Jihad and Expeditions, chapter titled "The Shares of the Horse," hadith no. 2863, and Muslim, hadith no. 1762, from the hadith of Ubaydullah bin Umar with this wording, and it is also found in Musnad Imam Ahmad, 2/41.