The first reading tells us a very strange story. After the Israelites passed through the Red Sea, in six short week Moses led them south down the length of the Sinai peninsula to Mount Sinai itself. He then, as God previously had told him to do, went up on the mountain for an important meeting with God. At that meeting God proposed entering into a covenant with the people. (It was like a marriage proposal.) God told Moses to ask the people if they would hearken to his voice, remaining faithful to the covenant.
Moses went down, and received assurance from the people that they would hold true to a covenant with God. After that, on the fiftieth day after the Passover meal in Egypt, God would induct the people into the covenant. (First, though, God meant to frighten the people to make them realize what a serious commitment they would make.)
Today’s reading tells us what happened four days before the covenant ceremony. God had Moses bring the people before Mount Sinai, then, he had the mountain erupt with great thundering and lots of smoke. It had the people flopping on the ground, calling for mercy. They got the idea behind it, which was that it wouldn’t pay for them to be untrue to God in their covenant.
In Deuteronomy 18:15 Moses reminded the people about how frightened they had been when God came to them on that thundering mountain He recalled how they had begged him to never let God again come to them in that terrifying way. In answer to their pleading, Moses said that God had promised when he came again he would not be scary. Instead, God would come as “A prophet like Moses I will raise up for them from among their own kinsmen, and I will put my words into his mouth.”
You’ll remember how when Jesus fed the five thousand with five loafs the people cried out, “This must be the prophet!” They were recalling the promise Moses made about a prophet like himself.