"Unlike other horsemen, the Bedouins only used mares for the hunt and for war. Stallions were used only for stud. Most colts were sold to horse dealers because only a few were needed for breeding. Breeding was only traced through the mares, not the studs. A pure-bred or "Asil" mare was highly revered. It was believed that only an Asil mare could carry one to victory in war."
Source: Arabian horse breed information