in which he teaches us to feel the sorrow of a person crushed under their master's heel
"These are the rules that you shall set before them: When you acquire a Hebrew slave". The Torah opens with the law that applies to a Hebrew slave, the first of all the laws to appear. The reason is that Torah plumbs the depths of human emotion, in particular that of the Israelite, in casese when a person is subject to the yoke of an individual similar to them. The Torah senses the deep, inner sorrow suffered by enslaved people that oppresses and embitters the spirit; enslavement is accompanied by domination, criticism and humiliation. This is all being caused by a similar creature, by another human being, and the person cannot reconcile himself or herself to the situation, human emotions beat within them at every moment: Why is he or she being oppressed and crushed under the master's heel, while the latter holds their head high and proud? In what way does he differ? Where not all people created by the Creator who provides for everyone, why has good fortune escaped them? These questions beat at their spirit and confuse their mind during every moment of every day. Their emotions gradually cool. The humanity within the person withers, dies at moments, until the spirit is finally entirely silenced, and the person becomes a living being with no feelings at all. Only animal needs remain; a person's vitality is reduced to feeling hunger and seeking how to sate it. The purpose of creation is, in a sense, diverted, for this was not the Creator's intent in creating humankind - the speaking and reflective being, capable of attaining the heights of wisdom. The Torah, therefore, had the law of the Hebrew slave precede all other laws, to place the restrictions necessary for us to prevent this. This is why it began by preventing a master from fully acquiring a Hebrew slave, stating that "he shall serve six years; in the seventh year he shall go free, without payment."
L'Yitzhak Re'akh, Mishpatim Reading Portion, p. 84, published by Eliyahu Hazzan, Jerusalem, 1993