كتاب الجهاد
Read the English translation first, with the original Arabic directly underneath.
Narrated AbuWahb:
The Prophet (ﷺ) said: Keep to every sorrel horse with a white blaze and white on the legs, or dark bay with a white blaze. He then mentioned something similar. Muhammad ibn al-Muhajir said: I asked him: Why was a sorrel horse preferred? He replied: Because the Prophet (ﷺ) had sent a contingent, and the man who first brought the news of victory was the rider of a sorrel horse.
عَلَيْكُمْ بِكُلِّ أَشْقَرَ أَغَرَّ مُحَجَّلٍ، أَوْ كُمَيْتٍ أَغَرَّ