Hi David,
Here are four sections of scripture which, I believe, illuminate what Jesus meant in those last three verses of Matt 23. Matthew, above the other gospel writers, quotes Isaiah's prophecies to the gentiles, as part of his entreaty to Jews to believe, however belatedly.
(NKJV) Mark 1:1 - 15
The beginning of the gospel of Jesus Christ, the Son of God.
As it is written in the Prophets: "Behold, I send My messenger before Your face, Who will prepare Your way before You. The voice of one crying in the wilderness: 'Prepare the way of the LORD; Make His paths straight.' "
John came baptizing in the wilderness and preaching a baptism of repentance for the remission of sins.
Then all the land of Judea, and those from Jerusalem, went out to him and were all baptized by him in the Jordan River, confessing their sins. Now John was clothed with camel's hair and with a leather belt around his waist, and he ate locusts and wild honey.
And he preached, saying, "There comes One after me who is mightier than I, whose sandal strap I am not worthy to stoop down and loose. "I indeed baptized you with water, but He will baptize you with the Holy Spirit."
It came to pass in those days [that] Jesus came from Nazareth of Galilee, and was baptized by John in the Jordan. And immediately, coming up from the water, He saw the heavens parting and the Spirit descending upon Him like a dove. Then a voice came from heaven, "You are My beloved Son, in whom I am well pleased."
Immediately the Spirit drove Him into the wilderness. And He was there in the wilderness forty days, tempted by Satan, and was with the wild beasts; and the angels ministered to Him.
Now after John was put in prison, Jesus came to Galilee, preaching the gospel of the kingdom of God, and saying, "The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel."
Matthew 21:32 - 45
"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, you did not afterward relent and believe him.
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. Now when vintage-time drew near, he sent his servants to the vinedressers, that they might receive its fruit. And the vinedressers took his servants, beat one, killed one, and stoned another.
Again he sent other servants, more than the first, and they did likewise to them. Then last of all he sent his son to them, saying, 'They will respect my son.' But when the vinedressers saw the son, they said among themselves, 'This is the heir. Come, let us kill him and seize his inheritance.' So they took him and cast [him] out of the vineyard and killed [i]him.[/i] Therefore, when the owner of the vineyard comes, what will he do to those vinedressers?" They said to Him, "He will destroy those wicked men miserably, and lease [i]his[/i] vineyard to other vinedressers who will render to him the fruits in their seasons."
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'? Therefore I say to you, the kingdom of God will be taken from you and given to a nation bearing the fruits of it. And whoever falls on this stone will be broken; but on whomever it falls, it will grind him to powder."
Now when the chief priests and Pharisees heard His parables, they perceived that He was speaking of them.
Matthew 26:29
"But I say to you, I will not drink of this fruit of the vine from now on until that day when I drink it new with you in My Father's kingdom."
[This last verse militates strongly against any suggestion that Jesus is going to come again in any other manifestation than He already has, even at His second coming, for the [i][b]purpose[/i][/b] of [u]evangelisation of unbelievers[/u].]
Luke 16:12 - 16, 29 - 31
"And if you have not been faithful in what is another man's, who will give you what is your own? No servant can serve two masters; for either he will hate the one and love the other, or else he will be loyal to the one and despise the other. You cannot serve God and mammon."
Now the Pharisees, who were lovers of money, also heard all these things, and they derided Him. And He said to them, "You are those who justify yourselves before men, but God knows your hearts. For what is highly esteemed among men is an abomination in the sight of God. The law and the prophets [i]were[/i] until John. Since that time the kingdom of God has been preached, and everyone is pressing into it.
"Abraham said to him, 'They have Moses and the prophets; let them hear them.'
And he said, 'No, father Abraham; but if one goes to them from the dead, they will repent.'
But he said to him, 'If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead.' " end of quotes
Jesus says that John the Baptist was the last [u]prophet[/u], even though He Himself, being the Word, explained all things to His disciples.