Juwaybir bin Sa'id, may Allah have mercy on him, said: A letter from our master Umar bin Abdul Aziz, may Allah have mercy on him, came to us in Khurasan, in which it was written: "I have been informed that some of your governors have reduced the shares of mules' offspring among the horses, whereas it has reached me through a trustworthy narrator from the Messenger of Allah, peace and blessings be upon him, that he assigned two shares each for all horses, both Arabian and mules' offspring. So distribute in the same way as the Messenger of Allah, peace and blessings be upon him, did. Allah Almighty has said in the Qur'an: «والخيل والبغال» , and by my oath, mules' offspring are not behind Arabian horses in effort. And peace be upon you."