Peter summarizes these verses in Acts 3:22-23, "Moses said, 'The Lord God will raise up for you a prophet like me from your brothers. You shall listen to him in whatever he tells you. And it shall be that every soul who does not listen to that prophet shall be destroyed from the people.'" This statement was part of Peter's address to the crowd in the temple after he heals the lame man in Jesus' name (Acts 3:6). Peter told them God fulfilled the promise of Deuteronomy 18:18 in Jesus Christ of Nazareth, who he says is the Holy and Righteous One, the Author of life.
It seems the people expected the Messiah to be the prophet God promised in Deuteronomy 18. In John 4:25, the Samaritan woman at the well told Jesus "I know that Messiah is coming. When he comes, he will tell us all things." Jesus responded to her by saying, "I who speak to you am he." Jesus claims to be the Messiah who will tell them everything.
Jesus publicly and privately makes that assertion many times. In John 8:28 Jesus says, "I do nothing on my own authority, but speak just as the Father taught me." In John 12:49, He adds "For I have not spoken on my own authority, but the Father who sent me has himself given me a command—what to say and what to speak." During the last supper, He told the eleven, "No longer do I call you servants...I have called you friends, for all that I have heard from my Father I have made known to you." (John 15:15)
Lord God, who but You would fulfill this promise by coming Yourself. We know all Your promises find their "Yes" in Jesus even this one in Deuteronomy 18. It is because of Jesus, for Your glory, we say Amen.
I think Isaiah understood Exodus 20:3, "You shall have no other gods before me." Don't you think he understood the first commandment just from reading this chapter?
Look at the number of times he says, "I am the LORD, and there is no other" or "besides me there is no God." He repeats himself in verses 14, 18, 21, and 22. God wants us to know there is no one like Him, so we have no reason to put anyone or anything before Him. In every way, He is the First.
Through the years, I have come to realize my breaking any of the other nine commandments is ultimately based on my not being completely settled upon the first commandment. If I am at peace with there being nothing comparable to Him, why would I ever discount Him in any way? If I genuinely believe that God has given me everything necessary for life and godliness, why would I seek anything outside the boundaries He establishes for His creation? Why would I search for anything else since the Messiah teaches me all things?
Father, I want to be a first commandment man. I desire to place nothing ahead of You. Holy Spirit, convict me quickly when anything is in the place of my Lord and my God.