45: Then answered one of the lawyers, and said unto him, Master, thus saying thou reproachest us also. 46: And he said, Woe unto you also, ye lawyers! for ye lade men with burdens grievous to be borne, and ye yourselves touch not the burdens with one of your fingers. 47: Woe unto you! for ye build the sepulchres of the prophets, and your fathers killed them. 48: Truly ye bear witness that ye allow the deeds of your fathers: for they indeed killed them, and ye build their sepulchres. 49: Therefore also said the wisdom of God, I will send them prophets and apostles, and some of them they shall slay and persecute: 50: That the blood of all the prophets, which was shed from the foundation of the world, may be required of this generation; 51: From the blood of Abel unto the blood of Zacharias, which perished between the altar and the temple: verily I say unto you, It shall be required of this generation. 52: Woe unto you, lawyers! for ye have taken away the key of knowledge: ye entered not in yourselves, and them that were entering in ye hindered. 53: And as he said these things unto them, the scribes and the Pharisees began to urge him vehemently, and to provoke him to speak of many things: 54: Laying wait for him, and seeking to catch something out of his mouth, that they might accuse him

45: Then answered one of the lawyers, and said unto him, Master, thus saying thou reproachest us also. 46: And he said, Woe unto you also, ye lawyers! for ye lade men with burdens grievous to be borne, and ye yourselves touch not the burdens with one of your fingers.

Parallel passage Matthew 23:4-5 For they bind heavy burdens and grievous to be borne, and lay them on men’s shoulders; but they themselves will not move them with one of their fingers. But all their works they do for to be seen of men. They make broad their phylacteries, and enlarge the borders of their garments.
The lawyers were the lawmakers who imposed man made laws upon the people. These works of the law were not done by the lawyers themselves, yet they pretended that they kept the law better than others! They made their phylacteries, or boxes they wore on their forehead larger than normal to keep more of the law in it. They enlarged the borders of their garments which contained the ribbon of blue reminding them of the Ten Commandment law. All of these things they did were for the purpose of being seen by men, not to please God.

47: Woe unto you! for ye build the sepulchres of the prophets, and your fathers killed them. 48: Truly ye bear witness that ye allow the deeds of your fathers: for they indeed killed them, and ye build their sepulchres.

The lawyers outwardly were trying to write laws or rules of behavior for the people to follow. God had sent His prophets with His Rules for the people and the fathers had killed them and disregarded God’s instructions through His prophets. Now the sons were not objecting but rather allowing what had been done. Instead of resurrecting the words of the old prophets, the sons were trying to hide or bury them.

49: Therefore also said the wisdom of God, I will send them prophets and apostles, and some of them they shall slay and persecute: 50: That the blood of all the prophets, which was shed from the foundation of the world, may be required of this generation; 51: From the blood of Abel unto the blood of Zacharias, which perished between the altar and the temple: verily I say unto you, It shall be required of this generation.

The lawyers thought that they could silence the prophets and apostles that God had sent by killing them! Since Abel until Zacharias wicked men had been killing righteous men that were sent to warn them of their wickedness. Now, God said enough. I will require their blood from this generation.

52: Woe unto you, lawyers! for ye have taken away the key of knowledge: ye entered not in yourselves, and them that were entering in ye hindered.

The lawyers had taken away the key of knowledge from the people. They had buried the writings of the prophets (key of knowledge – Old Testament Scriptures) and replaced them with their words. God’s Word was replaced with man’s word. When people tried to study the Scriptures themselves, they were forbidden to do so by the lawyers. Just like the Catholic Church placed the Bible on the index of Forbidden books and forbid the people to read it.

53: And as he said these things unto them, the scribes and the Pharisees began to urge him vehemently, and to provoke (#653) him to speak of many things: 54: Laying wait for him, and seeking to catch something out of his mouth, that they might accuse him

In order to stop Jesus from focusing His attention on them, the Pharisees etc tried to provoke Jesus by asking Him questions on many subjects with the intent to get Him to say something that they could use to accuse Him.