“The relation between body and soul, and altogether between the spirit of things and their corporeality, may be expressed by the example of a rider on horseback.
A rider who is in control and guides his steed can go much farther than he can go on foot.
How aptly then does the image of the Messiah as a poor man riding on a donkey describe the human predicament:
The divine spark borne and guiding, the physical donkey bearing up and waiting for guidance and power”
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose, p. 62 by Rabbi Adin Steinsaltz