¹² Then understood they how that he bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and of the Sadducees.

¹² Then they understood that he did not tell them to beware of the leaven of bread, but of the teaching of the Pharisees and Sad'ducees.

¹² Then they got it: that he wasn't concerned about eating, but teaching - the Pharisee-Sadducee kind of teaching.