21 And they went into Capernaum; and immediately on the sabbath he entered the synagogue and taught.
Jesus has been spending a lot of time in Galilee, he has just called four of the disciples on the shore of the Sea of Galilee. He goes to Capernaum which is one of fishing towns surrounding the large body of water. This was where Simon Peter lived and will become Jesus base of operations.
Jesus enters the Synagogue in Capernaum, the Synagogue is the religious community hub in each town or district, a place of prayer and study. Not to be confused with the Temple. The rise of the synagogues come from the Babylonian exile when Jews could not go to the Temple so schools of prayer were set up locally to teach the Law of Moses and also to keep the proclamations of the Prophets in mind. It was followed by a teaching on the scriptures that were read out. This is also where the rise of the Pharisees and Scribes came from, they were the teachers within these buildings. He enters on the Sabbath which was Saturday.
22 And they were astonished at his teaching, for he taught them as one who had authority, and not as the scribes.
Every week the locals would attend a “synagogue service” which is essentially the root of the Liturgy of the Word in the Mass. They have heard the scribes, pharisees and rabbi’s make their teachings every week but when Jesus teaches they are shocked by it. Jesus teaches “as one had authority” which is unlike the usual teachers of the scriptures there. This could imply that the typical teachers just used the teaching seat to push their own ideas, that they did not actually understand what they were talking about or what is more likely, that they did not teach much at all beyond general ideas of understanding.
When Jesus comes into teach he has a large advantage over the teachers of the Law. They cannot really go beyond the text itself without making mistakes but Jesus who has been sent by the Father and who is God in the flesh knows the substantial root of the meaning behind every line ever written down in scripture. He is their actual author after all. He can declare how and what things are to be understood in an authoritative manner that the scribes and pharisees simply could not.
23 And immediately there was in their synagogue a man with an unclean spirit;
The second appearance of “immediately” in so few verses. On average Mark uses the word “immediately” twice, he uses this word over forty times in his Gospel account. It drives home the action pact nature of each episode with Jesus, something to grab the attention of his Roman audience.
Within the synagogue itself is a man with an “unclean spirit”. The term for “unclean” is akathartos which in the Biblical context means ceremonial uncleanness, unessentially ungodly. Outside of the Biblical context like in Plato it has more of a physical dirt notion of uncleanness. The point of this articulation is that although to Jews there is only the Most High Spirit, Elohim, God and his servants, the pagan word had a grey view of the spiritual world. Telling someone that they had a spirit didn’t strike up much issue so Mark makes it clear that it is an ungodly spirit, this is helpful for his mainly Greco-Roman audience.
24 and he cried out, “What have you to do with us, Jesus of Nazareth? Have you come to destroy us? I know who you are, the Holy One of God.”
The possessed man cries out, asking what Jesus wants with them and even knows Jesus’ name. He seems to be aware that Jesus has something to do with the destruction of demons as well, claiming to know that he is “the Holy One of God”.
25 But Jesus rebuked him, saying, “Be silent, and come out of him!”
Jesus rebukes the unclean spirit, commanding him with nothing but his words to “be silent, and come out of him!” This is dramatically different to the elaborate exorcism practices of Second Temple Jewish Exorcists who required the invocation of Patriarchs, Angels and God.
Jesus tells the demon to be silent, some think this is to do with the messianic secret. He does not want the crowds to hear anything from the man that could further give away details about him, they must come to the understanding of who he is by faith in his actions, not the words of demon but this is just speculation. Others think Jesus is just further demonstrating his ability to command all of creation.
26 And the unclean spirit, convulsing him and crying with a loud voice, came out of him.
The demon possessed man convulses meaning he shakes his body in a somewhat violent manner. He cries with a loud voice before coming out of the mans body. Nothing is said of if the entity was visible after this fact, since Mark doesn’t mention it we can assume the demon is invisible and only “visible” within the actions of the man he possessed.
27 And they were all amazed, so that they questioned among themselves, saying, “What is this? A new teaching! With authority he commands even the unclean spirits, and they obey him.”
All the people in attendance at the synagogue are amazed, first with Jesus demonstration of his understanding of the written word of God and teaching it with authority and now to hit the point home harder, with only the words of his mouth he commands unclean spirits to dispossess a man they have forcefully taken control over. They ask the question “what is this?” again it is important to point out that exorcisms by Jews in this time and previous were not done by the authority of the exorcist, he was merely acting as an intermediary to higher powers like the Angels but Jesus in his own person has done what other require God to do. This should generate the question in the crowds minds, “If only God can do that and he just did it who is he?” They will not be able to answer this question until more signs give them the faith to though.
28 And at once his fame spread everywhere throughout all the surrounding region of Galilee.
This episode in the synagogue causes Jesus fame to spready everywhere through the region surrounding the sea of Galilee but since the people are not actually willing to come to the conclusion yet that Jesus is maybe more than a man, Jesus does not seem perturbed by the news spreading. It is just the news of a great exorcist not the news of the Messiah so it does not cause any issues for his future “hour” that he must endure as the Messiah.