“so that the people can hear when I speak with you.” It is commonly taught that the first time Israel got the Ten Commandments was when Moses came down Mount Sinai with them, but that is not correct. The first time Israel got the Ten Commandments was when God personally spoke them in a loud voice from Mount Sinai to the people of Israel at the foot of the mountain (Exod. 20:1-17). Then, after that, Moses went up on Mount Sinai and got the commandments on stone tablets—but Moses broke those first tablets (Exod. 24:15-18; 31:18; 32:19). Then Moses went up again to the top of Mount Sinai with a second set of stone tablets that God commanded Moses to make, and then God wrote the Ten Commandments again on that second set of tablets (Exod. 34:1-4; cp. Deut. 9:10-11, 15-17; 10:1-5).
God spoke the Ten Commandments in a loud voice to the Israelites between Moses’ third and fourth time up Mount Sinai. It was later, on Moses’ fifth trip up Mount Sinai, that God wrote the Ten Commandments on stone and gave them to him, but Moses broke those tablets. It was on Moses’ seventh and final trip up Mount Sinai that Moses got the Ten Commandments that he then put in the ark of the Covenant.
The Bible says in a number of places that the children of Israel heard the Ten Commandments spoken by God (cp. Exod. 20:22; Deut. 4:10-13, 15, 36; 5:4-6, 22-27; 18:16; Heb. 12:18-21). God spoke audibly to people on a number of occasions. He spoke to Adam and Eve in the Garden of Eden (Gen. 3:9ff), and He often spoke audibly to Moses (Num. 7:89). He also occasionally came into human form and appeared to people (see commentary on Acts 7:55).
The voice of God frightened the Israelites, so they asked that God not speak directly to them anymore, but that He would speak to Moses and Moses then could tell them what He said (Exod. 20:19-21). So it was that the rest of the Law of Moses was given by God to Moses who then told the people.
[For more information on Moses’ seven trips up Mount Sinai, see commentary on Exod. 19:3.]