Musannaf Ibn Abi Shaybah

Imam Awza'i (may Allah have mercy on him) said that Umar bin Abdul Aziz (may Allah have mercy on him) advised the commander appointed over the army that he should not ride any animal except such an animal whose pace is slower than all the animals present in the army.

Hazrat Umayyah al-Shami (may Allah have mercy on him) says that Hazrat Mak'hool and Hazrat Raja bin Haywah (may Allah have mercy on them) used to prefer the rear part of the army, and both of them would not separate from this part.

Hazrat Jumei’ bin Abdullah Al-Muqri (may Allah have mercy on him) narrates that Hazrat Umar bin Abdul Aziz (may Allah have mercy on him) forbade attaching iron to the end of the whip so that with it the animal may be made to run faster. And he (may Allah be pleased with him) also forbade (the use of) bridles.