Albert Barnes Commentary Matthew 23:30

"and say, If we had been in the days of our fathers, we should not have been partakers with them in the blood of the prophets." — Matthew 23:30 (ASV)

And say, etc. This they professed to say by rebuilding their tombs. They also, probably, publicly expressed their disapprobation of the conduct of their fathers. All this, in building and ornamenting tombs, was a profession of extraordinary piety. Our Lord showed them it was a mere pretense.