In this passage, Jesus calls Levi, a dirty, rotten tax collector who collaborates with Rome and skims money off the top for himself, he calls Levi to be a disciple. This man calls himself Matthew in Matthew and writes that gospel later on in life.
The Pharisees get mad at Jesus because he called a sinner and ate with him. Even John the Baptist's disciples are confused because Jesus never fasts. Jesus says that there is no need to fast because the bridegroom (himself) is here and we should celebrate. Soon, Jesus will go back to the Father in heaven, and then we can fast, but for now, celebrate and eat.
Next thing you know, it is Saturday, the Sabbath, and Jesus's disciples are hungry and picking grain as they walk through a field to eat, and the Pharisees get their panties in a wad because they consider that work. Jesus explains that the Sabbath is made to heal people and feed them, not to cause unnecessary rules that place restraints on people. Even David was fed the showbread from the tabernacle which was allowed for only priests to eat, but it was alright because David and his men were hungry and the priest had compassion on them.
In the last post, I had mentioned the paralyzed man that was lowered down to Jesus by his four friend through a roof (possibly Peter's roof). The Pharisees were mad because Jesus was forgiving the man for his sins. In that time, the only way anyone could be forgiven was on the Day of Atonement and that was when they went to the temple and offered a lamb to the priest to be slaughtered to take care of that person's sins for the past year. Now that Jesus is here, he is presenting a way to be forgiven without having to go to the Temple. Jesus, the Son of God, is finally here and will forgive sins because sinners are now covered under his blood, a permanent atonement. There is no more need for a priest, a sacrifice, because Jesus is it.
That is why Christians today should no longer anticipate the rebuilding of the temple. It is gone away with and Jesus is here and will never go away. For more, listen to this.
This passage mostly deals with the Pharisees' obsession with the rules. After the exiled Jews came back from Babylon to their homeland in Canaan, they wanted to make sure that they would never turn their backs on God again. So they looked at all of his rules in the Torah, built fences around them, and made sure that nobody would risk exile again. The problem is, they paid so much attention to the rules, that they forgot to notice God or his promise of a Savior from their sins. And when that Savior actually did come, they did not recognize him because they were too bogged down with rules that the Lord never intended when he gave his people the Law.
Jesus talked about old wineskins and new wineskins. God established Israel and his Old Covenant Laws for a time when he wanted his people to stand out from the rest of the countries and cultures and also to show them how imperfect they were as they tried to follow the rules in their own efforts. The wine of the Old Covenant had expanded the wineskin until it burst. Now, Israel and all of God's Church needed a new wineskin to handle the Law's fulfillment in Jesus. If you try to follow rules without following our Lord, then that is legalism and you will be crushed under your own efforts.
But if you get to know Jesus and rest in knowing that he has kept the law for you and offered the most perfect sacrifice for you, then you can truly relax and truly enjoy God. You can also properly obey God's law because you are no longer looking to your own efforts or penances. It is time to repent of our penances and simply love the Lord. Keeping the rules will happen as a result of that.