In Matthew 21, Jesus is in the temple preaching. The temple was the Jewish holy place, and the leaders of the temple did not take kindly to Jesus’ subversion of their own authority. They team up with the common religious teachers (the Pharisees) and approach Jesus demanding to know from where Jesus’ authority came:

Mat 21:23 Now when He came into the temple, the chief priests and the elders of the people confronted Him as He was teaching, and said, “By what authority are You doing these things? And who gave You this authority?”
Mat 21:24 But Jesus answered and said to them, “I also will ask you one thing, which if you tell Me, I likewise will tell you by what authority I do these things:
Mat 21:25 The baptism of John—where was it from? From heaven or from men?” And they reasoned among themselves, saying, “If we say, ‘From heaven,’ He will say to us, ‘Why then did you not believe him?’
Mat 21:26 But if we say, ‘From men,’ we fear the multitude, for all count John as a prophet.”
Mat 21:27 So they answered Jesus and said, “We do not know.” And He said to them, “Neither will I tell you by what authority I do these things.

Jesus cannot answer the question in verse 23 without some sort of legal action taken against him. The high priest of that day and supreme authority on religious matters, and he could also make arrests in the vicinity of the temple. It is important for Jesus to avoid answering: answering that his authority was from God would lead to arrest and answering that it did not come from God would undermine his ministry. Instead, Jesus focuses the question towards John the Baptist (who is well regarded as authoritative by Israel’s common people). Jesus had not yet reached the height of John’s ministry, so Jesus opts to draw a parallel between himself and John the Baptist. John the Baptist was not given a commission to teach from the leaders of the temple, nor was Jesus. John the Baptist taught per God’s authority, so did Jesus. By using the reputation of John the Baptist (who was also critical of religious leaders), Jesus leverages John’s authority to undermine the temple. The leaders of the temple were very afraid of losing power by contradicting popular opinion.

Jesus takes this a step further and undermines the temple leaders in front of the temple worshipers. They despised John the Baptist, and Jesus uses this fact to condemn them:

Mat 21:28 “But what do you think? A man had two sons, and he came to the first and said, ‘Son, go, work today in my vineyard.’
Mat 21:29 He answered and said, ‘I will not,’ but afterward he regretted it and went.
Mat 21:30 Then he came to the second and said likewise. And he answered and said, ‘I go, sir,’ but he did not go.
Mat 21:31 Which of the two did the will of his father?” They said to Him, “The first.” Jesus said to them, “Assuredly, I say to you that tax collectors and harlots enter the kingdom of God before you.
Mat 21:32 For John came to you in the way of righteousness, and you did not believe him; but tax collectors and harlots believed him; and when you saw it, you did not afterward relent and believe him.

This parable is directed at the temple leaders. The point Jesus is making is that evil people have a better chance of inheriting the kingdom of God than the temple leaders. This is a striking insult. The temple leaders prided themselves on their righteous acts and following the law. To Jesus, because the temple leaders were hypocrites and also did not believe John the Baptist, then they were worse than the people that they despised.

Jesus’ gospel of a coming kingdom of God, where God would kill the unrighteous and bless the righteous, is everywhere in this text. Not only is the appeal to John the Baptist’s ministry evidence (who taught the same thing), but also that Jesus is calling for the temple leaders to change their ways. This is not a “faith alone” text. It is not those who believe the right things, but those who perform who are the ones saved. The unrighteous temple leaders were to be counted among those God would kill.

To emphasize this point, Jesus continues:

Mat 21:33 “Hear another parable: There was a certain landowner who planted a vineyard and set a hedge around it, dug a winepress in it and built a tower. And he leased it to vinedressers and went into a far country.
Mat 21:34 Now when vintage-time drew near, he sent his servants to the vinedressers, that they might receive its fruit.
Mat 21:35 And the vinedressers took his servants, beat one, killed one, and stoned another.
Mat 21:36 Again he sent other servants, more than the first, and they did likewise to them.
Mat 21:37 Then last of all he sent his son to them, saying, ‘They will respect my son.’
Mat 21:38 But when the vinedressers saw the son, they said among themselves, ‘This is the heir. Come, let us kill him and seize his inheritance.’
Mat 21:39 So they took him and cast him out of the vineyard and killed him.
Mat 21:40 “Therefore, when the owner of the vineyard comes, what will he do to those vinedressers?”
Mat 21:41 They said to Him, “He will destroy those wicked men miserably, and lease his vineyard to other vinedressers who will render to him the fruits in their seasons.”

The imagery used is reminiscent of Isaiah 5. This parable lines up with God’s purposes in the Old Testament. God sought to create a special chosen people to be His own. Throughout the Bible, God was thwarted by consistent evilness and rejection from Israel. To Jesus, God would correct this soon by sending an army of angels to kill the wicked. This would leave only the righteous, a new righteous nation. In Jesus’ parable, the vineyard is Israel. The vintage-time is God returning to create a new Godly nation. The vinedressers are the religious leaders of Israel, who were meant to take care of the vineyard until harvest but who instead rebels. God is the vineyard owner, who sent servants that were killed by the vinedressers. Jesus strongly implies (and the religious leaders figure out later) that this parable means that God will kill the religious leaders.

Notice the imminence in the text. The “vintage-time” was drawing near. When Jesus was preaching against the temple leaders, he was not preaching destruction to a future generation who was not yet born. Jesus’ sermon was against the leaders of his own day. Jesus fully expected his prophecies to come to past shortly.

Another thing to note is that although Jesus probably was talking about himself as the “son”, many of the listeners might have equated the “son” with John the Baptist. Jesus’ ambiguity probably worked to his advantage with the common people. Jesus explains to the temple leaders his meaning:

Mat 21:42 Jesus said to them, “Have you never read in the Scriptures: ‘THE STONE WHICH THE BUILDERS REJECTED HAS BECOME THE CHIEF CORNERSTONE. THIS WAS THE LORD’S DOING, AND IT IS MARVELOUS IN OUR EYES’ ?
Mat 21:43 “Therefore I say to you, the kingdom of God will be taken from you and given to a nation bearing the fruits of it.
Mat 21:44 And whoever falls on this stone will be broken; but on whomever it falls, it will grind him to powder.”

By quoting Psalms 118, Jesus casts the temple leaders as the same type of people who were the enemies of King David. Jesus follows this up by ensuring that the temple leaders understand that the parables are about them and that they are to be the ones killed and excluded from the kingdom.

Mat 21:45 Now when the chief priests and Pharisees heard His parables, they perceived that He was speaking of them.
Mat 21:46 But when they sought to lay hands on Him, they feared the multitudes, because they took Him for a prophet.

After Jesus’ display, the crowds seem to empower Jesus. When the leaders first questioned Jesus, they were looking for some sort of charge to make against him. By the finale, Jesus’ boldness and popular appeal make Jesus a force with which to be reckoned. Jesus’ appeal to John the Baptist worked in leading the common people to equate one ministry with the other. This frightened the temple leaders.

The temple leaders and the Pharisees finally understand Jesus’ points and perhaps this adds to their plots to kill Jesus.