Musannaf Ibn Abi Shaybah

Hazrat Ata bin Dinar narrates that the Messenger of Allah, peace and blessings be upon him, said: Do not make the backs of your animals chairs for your conversations. Indeed, many mounts are better than their riders, for they are more obedient to Allah and remember Him much more.

Ibrahim Taimi states that Umar considered it undesirable to keep an animal standing for a long time.

Hazrat Kamil states that Hazrat Habib considered it undesirable to keep a mount standing for a long time and to beat it, even though it is one that does good.