Imam al-Shafi'i (may Allah have mercy on him) said in his old (opinion): "Allah Almighty commanded that they prepare against their enemy whatever strength they can and tethered horses, and Allah Almighty did not single out the Arab (pure-bred) horse to the exclusion of the hybrid horse. The Messenger of Allah (peace and blessings be upon him) permitted (eating) the meat of horses, and this (permission) covered (both) the hybrid and the Arab. He (peace and blessings be upon him) said: 'We have exempted you from the zakah on horses and slaves.' And he said: 'There is no zakah due from a Muslim on his horse or his slave.' So he (peace and blessings be upon him) counted the faras (a single horse) as part of the khayl (the genus of horses)."
Imam al-Shafi'i (may Allah have mercy on him) said: "It has been mentioned about the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) gave the Arab horse preference over the hybrid (in the spoils), and that Sayyiduna Umar (may Allah be pleased with him) also did so."
Imam al-Shafi'i (may Allah have mercy on him) said: "No one narrated this except Makhul, as mursal, and in our view no proof is established by a mursal report like it. Likewise, the report of Sayyiduna Umar (may Allah be pleased with him) is also mursal from Kulthum bin al-Aqmar."
Imam al-Shafi'i (may Allah have mercy on him) said: "Hammad bin Khalid informed us from Mu'awiyah bin Salih, from Abu Bishr, from Makhul, that the Prophet (peace and blessings be upon him) declared the Arab horse to be Arab and the hybrid to be hybrid (that is, he distinguished between the shares of the two)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / Q12882
It is narrated from Makhul (may Allah have mercy on him) that on the day of Khaybar the Messenger of Allah (peace and blessings be upon him) said: "Treat the Arab horse as Arab and treat the hybrid horse as hybrid."
This is the preserved (mahfuz) version, and it is mursal.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12882
"The horse has two shares and the hybrid horse has one share."
Abu Ahmad (Ibn Adi) said: No one but Ahmad (al-Jurjani) narrates this as connected, and his hadiths are not sound; it is as if he makes mistakes in them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12883
Khalid bin Ma'dan (may Allah have mercy on him) says: The Messenger of Allah (peace and blessings be upon him) "assigned shares: two shares for Arab horses and one share for the hybrid."
It is munqati' (broken chain); no proof is established by it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12884
It is narrated from Ibn al-Aqmar that the cavalry made a raid in Syria (al-Sham). The (Arab) horses caught up (with the enemy) the same day, and the kawadin (heavy non-Arab horses) caught up at forenoon. In command of the cavalry was al-Mundhir bin Abi Himmasah al-Hamdani. He gave the (Arab) horses preference over the kawadin and said: I will not treat what caught up the same as what did not catch up. This reached Sayyiduna Umar bin al-Khattab (may Allah be pleased with him), and he said: "May his mother be bereft of al-Wadi'i! She has indeed borne a true man. Carry it out as he said."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12885