Catena Aurea on Matthew 23:15: Gregory the Great

But forasmuch as hypocrites though they do ever crooked things, yet cease not to speak light things, and thus by their good instructions beget sons, but are not able to bring them up by good life, but the more they give themselves up to worldly works, the more willingly do they suffer those whom they have begotten to work the same. And because their hearts are hardened, these very sons whom they have begotten they do not own by any sign of the affection due.

Wherefore it is here said of the hypocrites, “And when he is made, ye make him twofold more the child of hell than yourselves.”