John Gill Bible Commentary

Fill ye up then the measure of your fathers. Of their sins; for there were bounds and limits set how far they should proceed, and no further; as yet they had not got to the end of their iniquity: their fathers had gone great lengths in sin, but their iniquity was not yet full, as is said of the Amorites, Gen 15:16 these their sons were to fill it up. They had shed the blood of many of the prophets; and indeed there were none of them but they had persecuted and abused, in one shape or another: some they entreated shamefully, others they beat: some they stoned, and others they put to death with the sword, or otherwise; and now their children were about to fill the measure brimful, by crucifying the Son of God, which they were at this time meditating and contriving; and by persecuting and slaying his apostles, and so would bring upon them the vengeance of God. The Jews well enough understood these words, which were spoken to them in an ironical way, and expressing what they were about, and what they would hereafter do, and what would be the issue and consequence of it: they have a saying (o), that "the holy blessed God does not take vengeance on a man, , "until his measure is filled up"; according to Job 20:22. Which the Chaldee paraphrase renders, "when his measure is filled up, then shall he take vengeance on him; and that this is Christ's sense, appears from what follows, (o) T. Bab. Sota, fol. 9. 1.