Deuteronomy 5:6

Here is the repetition of the ten commandments, in which observe, 1. Though they had been spoken before, and written, yet they are again rehearsed; for precept must be upon precept, and line upon line, and all little enough to keep the word of God in our minds and to preserve and renew the impressions of it. We have need to have the same things often inculcated upon us. See Phi 3:1. 2. There is some variation here from that record (Ex. 20), as there is between the Lord's prayer as it is in Mt. 6 and as it is Lu. 11. In both it is more necessary that we tie ourselves to the things than to the words unalterably. 3. The most considerable variation is in the fourth commandment. In Ex. 20 the reason annexed is taken from the creation of the world; here it is taken from their deliverance out of Egypt, because that was typical of our redemption by Jesus Christ, in remembrance of which the Christian sabbath was to be observed: Remember that thou wast a servant, and God brought thee out, Deu 5:15. And Therefore, (1.) "It is fit that thy servants should be favoured by the sabbath-rest; for thou knowest the heart of a servant, and how welcome one day's ease will be after six days' labour." (2.

— Matthew Henry's Concise Commentary (public domain)

I am the Lord thy God--The word "Lord" is expressive of authority or dominion; and God, who by natural claim as well as by covenant relation was entitled to exercise supremacy over His people Israel, had a sovereign right to establish laws for their government. [See on Exo 20:2.] The commandments which follow are, with a few slight verbal alterations, the same as formerly recorded (Exo. 20:1-17), and in some of them there is a distinct reference to that promulgation.

— Jamieson-Fausset-Brown Commentary (public domain)