The Lord said: “Woe to you who build the memorials of the prophets whom your fathers killed. Consequently, you bear witness and give consent to the deeds of your ancestors, for they killed them and you do the building. Therefore, the wisdom of God said, ‘I will send to them prophets and Apostles; some of them they will kill and persecute' in order that this generation might be charged with the blood of all the prophets shed since the foundation of the world, from the blood of Abel to the blood of Zechariah who died between the altar and the temple building. Yes, I tell you, this generation will be charged with their blood! Woe to you, scholars of the law! You have taken away the key of knowledge. You yourselves did not enter and you stopped those trying to enter.” When Jesus left, the scribes and Pharisees began to act with hostility toward him and to interrogate him about many things, for they were plotting to catch him at something he might say.
In today's Gospel, Jesus continued with His rebuke for the Pharisaic mentality. Jesus pointed out that the ancestors of the Pharisees persecuted and killed the prophets sent by God. When the Pharisees built memorials of the prophets, it might seem like an act of atonement. But Jesus said to them: "you bear witness and give consent to the deeds of your ancestors". What He meant by that is that the Pharisees were doing exactly what their ancestors did -- they persecuted Jesus the Son of God and plotted against Him.
Jesus then said to the scribes: "You have taken away the key of knowledge. You yourselves did not enter and you stopped those trying to enter." Jesus was referring to how they interpreted the Law in such a way that they made it inaccessible to the ordinary person. To make it worse, they did not observe it either. We should ask ourselves if we truly strive to live out the gospel? Would other people see in us what Jesus preached? Otherwise, we would become a barrier to evangelization.