Matthew 16:6

For he that takes heed of the leaven of the Pharisees and the Sadducees, does not observe the precepts of the Law and of the letter, and neglects the traditions of men that he may do the commandments of God. This is the leaven of which the Apostle speaks, A little leaven leaveneth the whole lump. (1 Cor. 5:6.) By every means also we should avoid that leaven which Marcion, Valentinus, and all the heretics had. For the nature of leaven is such, that when mixed with flour, that which seemed a little increases to a large quantity, and brings the whole mixture to its own flavour. Thus heretical doctrine if it have cast but a small spark into your breast, in a short time a mighty flame is raised, and drives the whole temper of the man along with it.

Because he said: take heed and beware etc. Here the teaching is set forth. By leaven he means corrupt doctrine; hence he does not mean the doctrine of the law, but the traditions of the Pharisees, which are called leaven, because just as from a …

And when His disciples were come to the other side, they had forgotten to take bread. Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees. Just as leaven is both sour and old, so too …

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.

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. They reasoned among themselves - What must we do then for bread, since we have taken no bread with us? Why reason ye - Why are you troubled about this?

But now they forgot; we will hope it was because their minds and memories were filled with better things. Note, Christ's disciples are often such as have no great forecast for the world. Here is the caution Christ gave them, to beware of the leaven of the Pharisees.

Beware of the leaven - What the leaven of Pharisees and Sadducees was has been already explained, see Mat 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.

In these verses we find our Lord assailed by the untiring enmity of the Pharisees and Sadducees. As a general rule these two sects were at enmity between themselves; in persecuting Christ, however, they made common cause. Truly it was an unholy alliance! Yet how often we see the same thing in the present day. Men of the most opposite opinions and habits will agree in disliking the Gospel, and will work together to oppose its progress. “There is no new thing under the sun” ( Ecclesiastes 1:9 ).

In these verses we find our Lord assailed by the untiring enmity of the Pharisees and Sadducees. As a general rule these two sects were at enmity between themselves; in persecuting Christ, however, they made common cause. Truly it was an unholy alliance! Yet how often we see the same thing in the present day. Men of the most opposite opinions and habits will agree in disliking the Gospel, and will work together to oppose its progress. “There is no new thing under the sun” ( Ecclesiastes 1:9 ). The first point in this passage which deserves special notice is the repetition which our Lord makes of words used by him on a former occasion. He says, “a wicked and adulterous generation seeketh after sign; and there shall no sign be given unto it but the sign of the prophet Jonah.” If we turn to the twelth chapter of this gospel and the thirty ninth verse, we shall find that he had said the very same thing once before. This repetition may seem a trifling and unimportant matter in the eyes of some. But it is not so in reality. It throws light on a subject which has perplexed the minds of many sincere lovers of the Bible, and ought therefore to be specially observed. This repetition shows us that our Lord was in the habit of saying the same things over again. He did not content himself with saying a thing once, and afterwards never repeating it. It is evident that it was his custom to bring forward certain truths again and again, and thus to impress them more deeply on the minds of his disciples. He knew the weakness of our memories on spiritual things; he knew that what we hear twice, we remember better than what we hear once. He therefore brought out of his treasury old things as well as new. Now what does all this teach us? It teaches us that we need not be so anxious to harmonize the narratives we read in the four Gospels, as many are disposed to be.