The Lord Jesus, again using the figure of a tree and its fruit (see chapter 7:17 -19), shows that a person reveals his own nature when he talks and acts.
What He said and did was good, proving that His nature was good. The Pharisees could not find anything wrong in what He did. They accused Him of breaking the law of the Sabbath, but He destroyed their arguments with just a few words. In spite of all His kindness, revealing His good nature, they came to accuse Him driving out demons by Beelzebub, the chief of demons. How to explain this?
The only possible explanation is that they were lying. Not lying out of ignorance, but out of spite. Their purpose was to undo the good reputation of the Lord Jesus Christ before the people, disparaging and defaming His person. These were evil fruits, which revealed the bad nature they owned. Their actions came from evil hearts.
Because of their evil nature they are called by the Lord a “brood of vipers”, the same term used by John the Baptist for the Pharisees and Sadducees when they came asking him to baptize them (chapter 3:7). Vipers are treacherous snakes with painful bites, often deadly. These Pharisees knew that Jesus was innocent, and had all the evidence to know that He was the Messiah, but had decided to become His enemies, and maliciously spread lies about His person.
When we speak and act, we express what we have deposited (enshrined) in our conscience (heart). If we keep good things, we are also going to say and do good things. Otherwise, they will be bad, as was the case with the Pharisees. The care that we should have with what we say becomes clear with what the Lord Jesus then says: on the Day of Judgment, men shall give account of "all idle words" they say.
An "idle word" is one that does no good at all, therefore becomes pernicious. This is serious: God knows our thoughts (ver. 25), the Lord declares that our words reveal our thoughts, informs us that they form a fair basis for the interpretation of our character, and reveals that we will be judged by them.
If an idle word is a basis for judgment, what about the bad words, lies, insults, or blasphemy, as these that the Pharisees were spreading? The Lord adds, "by thy words thou shalt be justified, and by thy words thou shalt be condemned": this statement is made in the second person singular, therefore it is directed personally to each one of us.
Those who are not saved (by their faith) will have to answer for their words before the final judgment. Those who were redeemed will have to answer before the judgment seat of Christ: these will not be punished because the punishment has already been done on the cross, but the sentencing will weigh on their reward.
James declares: "we all stumble in many things. If anyone does not stumble in word, he is a perfect man, able also to bridle the whole body” (James 3:2). Self-control begins by controlling the tongue, and this is very important because of the repercussions that a careless, idle word, can have.
Some of the scribes and Pharisees, feeling the justice of what the Lord Jesus said, and burning with His whipping, tried to save face by grumbling, "Teacher, we want to see a sign from You”. They were careful to call Him "master", or Rabbi, but the content of the sentence suggests that in their opinion He might be a false teacher, whose authority had yet to be proven.
It was a temerity on their part to suggest that He had given no evidence yet of His authenticity, after all that the Lord Jesus had spoken and done publicly, even right in front of them. Their hypocrisy was evident, for if what they had already witnessed was not enough, nothing else would convince them. To demand miraculous signs before you believe is not an attitude that pleases God. The Lord Jesus later said, "blessed are those who have not seen and have believed." The signs will be seen and recognized after you believe.
The reply from the Lord Jesus to these religious hypocrites came immediately and was long and scathing:
They were "a wicked and adulterous generation", evil was characteristic of their character, revealed by the manner in which they treated the Lord Jesus. Adultery was their infidelity to God: religious on the outside, inside they were selfish to the point of rejecting God's Son who was among them.
No other sign would be given them except for that of the prophet Jonah. This prophet had spent three days and three nights in a great fish, and after that was expelled, unscathed, to resume his evangelistic mission in wicked city of Nineveh. It was really a supernatural event, a miracle of God. It was the precedent of an even more remarkable miracle: the death, the burial of Jesus Christ for three days and three nights, and His resurrection to start the preaching the Gospel to the whole world.
On the day of final judgment (after the "Millennium" - Revelation 20:11-15), the men of Nineveh will rise again (this is the second resurrection – that of the lost) with them and condemn them, because they (the Ninevites) repented with the preaching of Jonah, while these religious did not believe in Someone greater than Jonah.
Also the Queen of the South (this refers to the Queen of Sheba, at the time of Solomon) will condemn them on that day because she went from the ends of the Earth to Jerusalem to hear Solomon, and He is greater than Solomon.
They are like a man who was demon-possessed, with only one demon to begin with, but this left and returned with seven more, even worse than him. As a result, the actions of this man became even worse than they were before.
Some believe that this parable does not seem to fit the Pharisees from that era too well, and so interpret "So shall it also be with this wicked generation " as a description of the history of Israel:
The man would represent the nation of Israel, and the unclean spirit would be idolatry involving them since the slavery in Egypt until the captivity in Babylon.
Then the people left idolatry, corresponding to the day when the unclean spirit left the man. The people cleaned the house, but it was empty because it did not receive the Messiah sent to them. So it continues and will continue until the Antichrist appears, in the seven years of tribulation.
During the tribulation, the nation will worship the Antichrist, as the rest of the world, and it will be much worse than the idolatry of antiquity. They will suffer the plagues of that period and its state will become much worse than at the beginning; judgment will be made on the return of the Messiah, when a faithful remnant will be saved from its enemies, and the rest will be destroyed.
There is a difficulty, however. Paul teaches that when you get the "fullness of the Gentiles", which is when the Church is complete and is raptured, "all Israel will be saved" (Romans 11:25 and 26).
Another interpretation, more acceptable, is that He is referring to the "reformed": typically a person coming out of conviviality with the world, improves his behaviour, even makes a profession of faith in Christ and is received in communion in the Church. If there was not a genuine conversion he does not have the Holy Spirit, and is like an "empty house". One day he returns to the world and becomes much worse than he was before. This is consistent with Hebrews 6:4-6 and 2 Peter 2:17-22.
These Pharisees said they were faithful to God, but in reality were far away from Him, and ended up by killing his Son.
33 "Either make the tree good and its fruit good, or else make the tree bad and its fruit bad; for a tree is known by its fruit.
34 Brood of vipers! How can you, being evil, speak good things? For out of the abundance of the heart the mouth speaks.
35 A good man out of the good treasure of his heart brings forth good things, and an evil man out of the evil treasure brings forth evil things.
36 But I say to you that for every idle word men may speak, they will give account of it in the day of judgment.
37 For by your words you will be justified, and by your words you will be condemned."
38 Then some of the scribes and Pharisees answered, saying, "Teacher, we want to see a sign from You."
39 But He answered and said to them, "An evil and adulterous generation seeks after a sign, and no sign will be given to it except the sign of the prophet Jonah.
40 For as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth.
41 The men of Nineveh will rise up in the judgment with this generation and condemn it, because they repented at the preaching of Jonah; and indeed a greater than Jonah is here.
42 The queen of the South will rise up in the judgment with this generation and condemn it, for she came from the ends of the earth to hear the wisdom of Solomon; and indeed a greater than Solomon is here.
43 "When an unclean spirit goes out of a man, he goes through dry places, seeking rest, and finds none.
44 Then he says, 'I will return to my house from which I came.' And when he comes, he finds it empty, swept, and put in order.
45 Then he goes and takes with him seven other spirits more wicked than himself, and they enter and dwell there; and the last state of that man is worse than the first. So shall it also be with this wicked generation."
Gospel of Matthew, chapter 12 verses 33 to 45