Matthew 23:31

Wherefore ye witness to yourselves, that ye are sons of them that slew the prophets. Fill ye up then the measure of your fathers. Ye serpents, ye offspring of vipers, how shall ye escape the judgment of hell?

Not merely were those men the physical descendants of those who persecuted and slew the prophets, they were also their moral and spiritual sons as well, full of fraud and deceit, fit architects for fashioning a cross for the Beloved.

Fill ye up then the measure of your fathers. This is irony. They had passed the point of no return; and like Balaam of old, they could not have gone back if they had tried at this point, although there was no possibility of their even trying. As the angel said to Balaam, "Go with the men!" so Jesus here commanded them to do the thing they had already purposed to do, and from which there was now no longer any possibility of drawing back. Evil hearts had already committed the foul murder which their external actions would only confirm before the week ended.

There is a stark contrast between the wickedness of the men who killed Christ and that of Balaam (Numbers 22:34). Balaam tried to abort his evil mission but could not. These men did not even try to abort theirs. Over against Balaam, an angel with a drawn sword gave the summary command, "Go with the men!" How that must have chilled his heart with fear and dread. In every evil course, there is a point where the sinful soul becomes apprehensive and would draw back but cannot. There is a threshold which, when crossed, admits of no complete spiritual returning. What a terrible moment for the sinful that must be! It is an evil hour, fraught with the pangs of conscience and the fear of hell, but void of any place for repentance even though sought bitterly with tears, as in the case of Esau. Yet such an awareness of the horrors of evil seems never to have come to the Pharisees. They were already dead spiritually. The very Christ of God stood before them in an amazing drama of outraged innocence and thundered the sentence: "Fill ye up then the measure of your fathers!" There was no evidence that they heard him. Spiritual "rigor mortis" had already set in!

Ye serpents ... Much of Jesus' language was metaphorical, but this was one of the strongest ever used. Herod was called a fox; the opponents of the gospel were called "wolves" in sheep's clothing; but the Pharisees were compared to the most detestable of all creatures, serpents, and poisonous ones at that, VIPERS! The judgment of hell was a reference to the final overthrow of the wicked in the lake of fire (see the margin of the ASV). The question, "how shall ye escape" ... is actually an affirmation that they shall not escape.