Demons came out of many people, shouting out, "You are the son of God!" He sternly forbade them to be speak, because they knew Him to be the Messiah." Luke 4:41 "You should tell people about Jesus."
Have you ever been told this? In the Bible Belt where I live, this message was impressed upon us time and time again while growing up. As an aside, I haven't heard it much in recent days but that could simply be because the circles I have fellowship in have changed. Nevertheless, it is a basic principle and an accepted fact that one of our many duties as evangelical Christians is to tell people the good news about Jesus. But what is that good news? That is a very important question. Here we have a very odd situation where a demon declares the truth about Jesus, that He is the son of God, and Jesus rebukes the demon, telling it to be quiet. I am surprised that I have no recollection of church people in my experience who have asked the question "why?" Why should a demon be rebuked for doing what Christians are commanded to do? This scenario presented by Luke can only make sense when we realize that the phrase "son of God" did not infer deity but was rather another name for the Messiah. There were other "sons of God" in Israel's history like David and Solomon, people whom cooperated with God and were used to accomplish His purposes. Luke has already told us about the family line of Joseph, Jesus' adopted earthly father, whose family lineage went all the way back to Adam whom Luke refers to as "the son of God". But Luke certainly doesn't imagine that we should think of Adam in any way as being divine. Adam was simply created by and in the image of God in order to carry out God's purposes, thus he is God's "son". But in this sense, we are all God's children. However, Jesus has come, in part, to make this true in a way that it had never been before.
So what was the demon doing by making this declaration and why did Jesus tell it to shut up? I think the short answer is that they were attempting to blow Jesus' cover. It could be that these evil spirits were speaking impulsively and thoughtlessly in the presence of Jesus and were not being intentional, but the result would have been the same. Jesus seems keen to do His work and allow the work to speak for itself. Jesus didn't overtly say in public "I am the Messiah" but seemed to want people to see what He was doing and work it out for themselves. Even when Jesus stands before Pilate and Is asked directly "Are you the King of the Jews?", Jesus simply says "it is as you say" or "those are your words". Clearly, Jesus isn't denying it, but he also isn't trumpeting it either. I think this may have been for a few reasons: First of all, Jesus wanted people to work things out for themselves. When we work things out and arrive at a conclusion, it becomes a much more solid conviction than it would have been if someone simply impressed upon us a position that they thought we should take. Secondly, overt claims about being the Messiah was bound to draw unwanted attention not only from Rome but from the Jewish authorities as well. Thirdly, the Jewish expectation of the Messiah in Jesus' day may have been so strong that Jesus, having made overt claims to be that Messiah, might have been forcibly pressured to conform to that expectation. The crowds do in fact attempt to force Jesus to become king in their own fashion at at least one point. (John 6:15). But Jesus is in fact the Messiah and believes Himself to be the Messiah and His public baptism confirmed this vocation. But Jesus thoroughly intends to reshape the vision of what a Messiah should look like and do. And that is why Jesus' Messiahship is so controversial and divisive. There may be nothing quite like redefining national identity to bring about a civil war. And the Israel of Jesus' day was barreling its way toward war and wars of many sorts. And while Jesus' Messiahship acts as a catalyst for some outbursts of the mounting tensions, Jesus stands alone in the fray, calling for a new way forward, a way of peace and self-sacrifice. A way that He must take alone but also calls others to follow after Him (Mark 10:38). But this calls for wisdom and tact, not outbursts of volatile claims by rouge and destructive spirits. Therefore, Jesus tells the demons to shut up, and He prays that His deeds will speak loudly. The Messiah is here, but He is not what we expected.