Luke 11:51, commentary and pictures

The blood to be required stretches from Abel to Zacharias, who perished between the altar and the temple, that is, the blood of all the prophets shed from the foundation of the world. The generation confronting Christ, the Jewish nation Jesus addressed before multitudes, is held accountable for that accumulated guilt through history.

That accountability stands within the long history of Israel's guilt, with successive generations growing more guilty by repeatedly rebelling against God's requirements, perverting what He had entrusted to them, and distorting or displacing sacred things. Outward reverence for the prophets' tombs and claims to piety did not distinguish them from their fathers, because they continued the same hostility, cruelty, and resistance to God's messengers, even judging others while failing to keep the law themselves.

They followed the course of their fathers by rejecting the light, truth, warnings, blessings, and mercy God had given, including the Son of God, so that God's sending of prophets and apostles was met with killing and persecution. The denunciation is made more awful because Jesus restrained His own prerogatives and power and reviled not again when reviled, and because the Lord had long borne patiently with deception and impiety, inflicting less punishment than sins deserved, which did not remove accountability. By persisting in sin they filled up the measure of iniquity, showed themselves finally impenitent and stubbornly opposed to truth despite warnings and blessings, and brought God's punishment and judgment upon them, which serves as an example to the world and proves before a law-transgressing world that He is God and beside Him there is none else.