Albert Barnes Commentary Matthew 23:32

"Fill ye up then the measure of your fathers." — Matthew 23:32 (ASV)

Fill ye up then, etc. This is a prediction of what they were about to do. He would have them act out their true spirit, and show what they were, and demonstrate to all that they had the spirit of their fathers. This was done by putting him to death, and persecuting the apostles.

The measure. The full amount, to make it complete. By your slaying me, fill up what is lacking of the iniquity of your fathers until the measure is full, the national iniquity is complete, as much has been committed as God can possibly bear, and then shall come upon you all this blood, and you shall be destroyed (Matthew 23:34–35).