So you, fill up what your fathers left unfinished.
Jesus’ words here sound like a prophetic and condemning declaration. He says that they are not only following the conduct of their ancestors, but will soon complete their evil, bringing it to its final limit by rejecting and crucifying the Son of God. The phrase “Fill up what your fathers left unfinished” means: you are already walking the same path; continue until the point where God’s patience will come to an end and judgment will come. This is not an invitation to evil, but a prophetic foretelling that they themselves will reach the full measure of sin.