The Harmony Of The Gospels by St. Augustine
Chapter LII.--Of Matthew's Agreement with Mark in the Statement About the Leaven of the Pharisees, as Regards Both the Subject Itself and the Order of Narrative.
107. Matthew proceeds: |And He left them, and departed. And when His disciples were come to the other side, they forgot to take bread. Then Jesus said unto them, Take heed, and beware of the leaven of the Pharisees and of the Sadducees;| and so forth, down to where we read, |Then understood they that He bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and of the Sadducees.| These words are recorded also by Mark, and that likewise in the same order.