Exodus 18:16

I do make them know. Some commentators have taken the reference to statutes and laws as proof that the visit of Jethro occurred after the giving of the law at Sinai. Others have pointed out that the practice described in this passage would not have been necessary after the giving of the law, and that its existence at the time of Jethro’s visit fixes the visit as having occurred before the law was formally proclaimed to Israel. The latter explanation seems preferable. God had not left His people for thousands of years without moral law. Cain knew that murder was sin (Gen. 4:8-13), Shem and Japheth demonstrated acquaintance with the law by shunning indecency (Gen. 9:23), Abraham observed God’s commandments (Gen. 26:5), and even the Philistine king Abimelech knew that adultery was “a great sin” (Gen. 20:9). The mentioning of “my commandments, my statutes, and my laws” (Gen. 26:5) in the time of the patriarchs is therefore not anachronistic, but shows clearly man’s knowledge of such divinely imparted laws before Sinai. Moses, who during the 40 years of his desert sojourn had recorded the history of God’s dealings with the patriarchs, must have been well acquainted with the moral principles set forth in the book of Genesis.