al-Walid bin 'Utba al-'Ashj'y الوليد بن عتبة الأشجعي أبو العباس الدمشق · Jihad (Kitab Al-Jihad)

The Messenger of Allah (ﷺ) sent us along with an army towards Najd, and he sent a detachment of that army (to face the enemy). The whole army got twelve camels per head as their portion, but he gave the detachment one additional camel (apart from the division made to the army). Thus they got thirteen camels each (as a reward).