John Calvin on Exodus 25:16

16. And thou shalt put into the ark the testimony. The title of “the testimony,” which is often given to the law, indicates that something more is contained in it than the rule of a just and holy life; viz., the compact whereby God bound Himself to His people, and His people to Himself; therefore the words “the table of the covenant,” are afterwards used instead of “the testimony.” Thus the word עדת, “A testimony, or public evidence,” from עוד, to affirm, or testify. — W gneduth, in this passage, and similar ones, is equivalent to a contract, which is commonly called a convention In this sense the Prophet in Psalm 114 calls by the name of testimonies, not only the Commandments, but whatever God hath delivered by the hand of Moses for the salvation of His people. In Psalm 14:7, the word testimony is added as if in explanation of the word law: “The law of the Lord is perfect; the testimony of the Lord is sure;” as in Isaiah 8:20, where it is said, “To the law and to the testimony,” it is not that two different things are referred to, but the utility of the law is commended, because it contains all that God would have testified to His people.