Take heed ... - That is, be cautious, be on your guard.

The leaven of the Pharisees and Sadducees - Leaven is used in making bread.

It passes secretly, silently, but certainly through the mass of dough. See the notes at Matthew 13:33. "None can see its progress." So it was with the doctrines of the Pharisees. They were insinuating, artful, plausible. They concealed the real tendency of their doctrines; they instilled them secretly into the mind, until they pervaded all the faculties like leaven.

They reasoned ... - The disciples did not understand him as referring to the doctrine of the Pharisees and Sadducees, because the word "leaven" was not often used among the Jews to denote doctrines, no other instance of this use of the word occurring in the Scriptures. Besides, the Jews had many particular rules about the leaven (yeast) which might be used in making bread. Many held that it was not lawful to eat bread made by the Gentiles; and the disciples, perhaps, supposed that he was cautioning them not to procure a supply from the Pharisees and Sadducees.

O ye of little faith! - Jesus, in reply, said that they should not be so anxious about the supply of their temporal wants. They should not have supposed, after the miracles that he had performed in feeding so many, that he would caution them to be anxious about procuring bread for their necessities. It was improper, then, for them to reason about a thing like that, but they should have supposed that he referred to something more important. The miracles had been full proof that he could supply all their wants without such anxiety.

Beware of the leaven - What the leaven of Pharisees and Sadducees was has been already explained, see Matthew 16:1. Bad doctrines act in the soul as leaven does in meal; they assimulate the whole Spirit to their own nature. A man's particular creed has a greater influence on his tempers and conduct than most are aware of. Pride, hypocrisy, and worldly-mindedness, which constituted the leaven of the Pharisees and Sadducees, ruin the major part of the world.

Then Jesus said unto them,.... Either taking occasion from the disciples observing that they had forgot to take bread with them, or on account of what passed between him and the Pharisees and Sadducees, he gave the following advice to his disciples;

take heed and beware of the leaven of the Pharisees and of the Sadducees. Mark, instead "of the leaven of the Sadducees", says, "the leaven of Herod"; either because Christ might caution against all three; or because the Sadducees were generally Herodians, taking Herod to be the Messiah; or were on his party, or for his government, which the Pharisees disliked; and the Herodians were generally Sadducees. By "the leaven" of these is meant their doctrine, as appears from Matthew 16:12. The doctrines the Pharisees taught were the commandments and inventions of men, the traditions of the elders, free will, and justification by the works of the law: the doctrine of the Sadducees was, that there was no resurrection of the dead, nor angels, nor spirits: now because they sought secretly and artfully to infuse their notions into the minds of men; and which, when imbibed, spread their infection, and made men sour, morose, rigid, and ill natured, and swelled and puffed them up with pride and vanity, Christ compares them to leaven; and advises his disciples to look about them, to watch, and be on their guard, lest they should be infected with them.

Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees.

16:6 Beware of the leaven, etc. The teaching and influence which spreads like leaven. See Mt 16:12. The figure of the leaven was suggested by their need of bread.

Sadducees. Mark instead of of the Sadducees, says, of Herod (Mr 8:15). Herod and his followers were Sadducees.

16:6 Beware of the leaven of the Pharisees - That is, of their false doctrine: this is elegantly so called; for it spreads in the soul, or the Church, as leaven does in meal. Luke 12:1.

16:5-12 Christ speaks of spiritual things under a similitude, and the disciples misunderstand him of carnal things. He took it ill that they should think him as thoughtful about bread as they were; that they should be so little acquainted with his way of preaching. Then understood they what he meant. Christ teaches by the Spirit of wisdom in the heart, opening the understanding to the Spirit of revelation in the word.