Matthew 16:6

ὁρᾶτε καὶ προσέχετε : an abrupt, urgent admonition to look out for, in order to take heed of, a phenomenon of very sinister import; in Scottish idiom “see and beware of”. More impressive still in Mk.: ὁρᾶτε, βλέπετε, a duality giving emphasis to the command (ἀναδίπλωσις, ἐμφαίνουσα ἐπίτασιν τῆς παραγγελίας, Euthy.). ζύμης, leaven, here conceived as an evil influence, working, however, after the same manner as the leaven in the parable (Matthew 13:33). It Is a spirit, a zeitgeist, insinuating itself everywhere, and spreading more and more in society, which Jesus instinctively shrank from in horror, and from which He wished to guard His disciples. τῶν φαρ. καὶ Σαδ : one leaven, of two parties viewed as one, hence no article before Σαδ. Two leavens separately named in Mk., but even there juxtaposition in the warning implies affinity. The leaven of Pharisaism is made thoroughly known to us in the Gospels by detailed characterisation. Sadducaism very seldom appears on the stage, and few words of Jesus concerning it are recorded; yet enough to indicate its character as secular or “worldly”. The two classes, antagonistic at many points of belief and practice, would be at one in dislike of single-hearted devotion to truth and righteousness, whether in the Baptist (Matthew 3:7) or in Jesus. This common action in reference to either might not be a matter of arrangement, and each might come with its own characteristic mood: the Pharisee with bitter animosity, the Sadducee with good-natured scepticism and in quest of amusement, as when they propounded the riddle about the woman married to seven brothers. Both moods revealed utter lack of appreciation, no friendship to be looked for in either quarter, both to be dreaded.