Musannaf Ibn Abi Shayba 28:663

Ibn ‘Uyaynah narrated to us, from al-Aswad ibn Qays and Ibrahim ibn al-Muntashir, from Ibn al-Aqmar, who said: The cavalry raided in al-Sham, and the Arabian horses caught up [to the enemy] on their day, while the pack horses (kawādin) caught up the next morning. Ibn Abi Humsa said: "I will not make the one who caught up equal to the one who did not catch up." So he wrote to ‘Umar. ‘Umar said: "May the mother of the Wada‘i be bereaved of him! He has indeed reminded [me] of it. Execute it according to what he said."