Fear thy God - Yahweh was the Lord and Master of His people. To treat a Hebrew as a slave was therefore to interfere with the rights of Yahweh. Compare Romans 14:4.

Thou shalt not rule over him with rigor - What is rigorous service? "Service which is not determined, and service whereof there is no need." This is the definition given by the Jews; but much more is implied in this command than is expressed here. Labour beyond the person's strength, or labor too long continued, or in unhealthy or uncomfortable places and circumstances, or without sufficient food, etc., is labor exacted with rigour, and consequently inhuman; and this law is made, not for the Mosaic dispensation and the Jewish people, but for every dispensation and for every people under heaven.

Thou shalt not rule over him with rigour,.... As the Egyptians ruled over the Israelites, and made them to serve, Exodus 1:13; where the same word is used as here, and seems designed to put them in mind of it, that so they might abstain from such usage of their brethren, which they had met with from their most cruel enemies; it signifies tyranny and oppression, treating them with great severity, laying hard and heavy tasks and burdens upon them they could not bear; enjoining them things they could not perform, and ordering them to do what were unnecessary, and without any limitation with respect to time:
but shalt fear thy God; that has been good to thee, and has brought thee out of hard and rigorous bondage in Egypt; and which should be remembered with thankfulness, and they should fear to offend so good a God by using a brother cruelly.

Fear thy God - Though thou dost not fear them who are in thy power, and unable to right themselves, yet fear that God who hath commanded thee to use them kindly, and who can and will avenge their cause, if thou oppress them.