(15) He charged them.--The verb is in the imperfect tense, and implies that the command was more than once repeated. Hence they, too, "were reasoning," more than once, what was the meaning of the precept on which so much stress was laid.

The leaven of Herod.--The words imply the presence among the questioners of Mark 8:11 of others besides the Pharisees. On the connection between the "leaven of Herod" and that of "the Sadducees" in Matthew 16:6, see Note on that verse.

Verse 15. - Beware of the leaven of the Pharisees and the leaven of Herod. St. Matthew (Matthew 15:6) says, "Beware of the leaven of the Pharisees and Sadducees;" thus St. Mark identifies the leaven of the Sadducees with that of Herod. "Leaven" here means "doctrine." They were not to beware of this, so far as the Pharisees rightly taught and explained the Law of Moses; but only so far as they corrupted that Law by their own vain traditions, contrary to the Law of God, St. Luke (Luke 12:11) calls this leaven "hypocrisy;" because the Pharisees only regarded outward ceremonies, and neglected the inward sanctification of the Spirit. St. Jerome says, "This is the leaven of which the Apostle speaks where he says, 'A little leaven leaveneth the whole lump.' Marcion and Valentinus and all heretics have had this kind of leaven, which is on every account to be avoided. Leaven has this property, that, however small it may be in quantity, it spreads its influence rapidly through the mass. And so if only a little spark of heretical doctrine be admitted into the soul, speedily a great flame arises, and envelopes the whole man."

8:11-21 Obstinate unbelief will have something to say, though ever so unreasonable. Christ refused to answer their demand. If they will not be convinced, they shall not. Alas! what cause we have to lament for those around us, who destroy themselves and others by their perverse and obstinate unbelief, and enmity to the gospel! When we forget the works of God, and distrust him, we should chide ourselves severely, as Christ here reproves his disciples. How is it that we so often mistake his meaning, disregard his warnings, and distrust his providence?And he charged them,.... When they were in the ship, and had just recollected themselves, that they had took no care to bring any provisions with them:

saying, take heed, beware of the leaven of the Pharisees; and of the leaven of Herod: in Matthew, instead of "the leaven of Herod", it is read, "the leaven of the Sadducees": which are either the same, Herod and his courtiers being Sadducees, or favourers of them; or the Sadducees being sticklers for Herod, and his government, which the Pharisees had no good opinion of; or else distinct from one another; and so Christ cautions against the doctrines of the Pharisees, which regarded the traditions of the elders, and of the Sadducees, concerning the resurrection, and of the Herodians, who thought Herod to be the Messiah; and against the unreasonable request and demand of them all to have a sign from heaven, in proof of his own Messiahship; See Gill on Matthew 16:6.