Then understood they,.... Without any further explication of his sense and meaning,how that he bade them not beware of the leaven of bread: which sense they first took him in; imagining, because the Pharisees were very particular and precise what sort of leaven they made use of , that Christ forbad them buying bread that was made with leaven according to their directions: and since their rules in everything prevailed much in all places, they were concerned what bread they must, or could buy; but now they perceived that he did not speak of this, but of the doctrine of the Pharisees and of the Sadducees.
It was very common with the Jews to call the corruption and vitiosity of nature by the name of hoyebv rwav, "leaven in the lump": hence our Lord calls their doctrine so, because it proceeded from thence, and was agreeable thereunto; and uses the phrase on purpose to expose it, and bring it into neglect and contempt.
Misn. Pesach, c. 2. sect. 2, 3. T. Hieros. Sabbat, fol. 3. 3. T. Hieros. Beracot, fol. 7. 4. T. Bab. Beracot, fol. 17. 1. Bereshit Rabba, fol. 29. 4. Caphtor, fol. 38. 2. Tzeror Hammor, fol. 73.