(17) Have ye your heart yet hardened?--The question is peculiar to St. Mark, as are also the two first questions in Mark 8:18. The expression of indignant astonishment is characteristically more vivid and emphatic in St. Mark's report.

Verse 17. - And when Jesus knew it (καὶ γνοὺς ὁ Ἰησοὺς) - literally and far more correctly, and Jesus perceiving it - he saith unto them, Why reason ye, because ye have no bread? Jesus perceived the direction in which their thoughts were moving, by the power of his divinity. It is as though he said, "Why reason ye because ye have no bread, as though I was referring to natural things, and speaking concerning bread for the body, and wishing you to be anxious about that; as though I could not provide that for you, if nccessary, just as easily here on the sea as I did just now in the desert?" Dr. John Lightfoot ('Hebrew Excrcitations on St. Matthew,' vol. 2:p. 201) says, "The rule of the Jews was very strict as to the kind of leaven that was to be used; and the disciples supposed that our Lord was alluding to this when he cautioned them to beware of the leaven of the Pharisees." Perhaps they also thought that our Lord was conveying a silent reproof to them for not having brought a sufficient supply of bread with them. The whole incident, while it shows their transparent simplicity of character, exhibits also their dulness of apprehension.

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 when Jesus knew it,.... As he did immediately, by his omniscience; for as he knew the thoughts and reasonings of the Scribes and Pharisees, Matthew 9:4, so he did those of his own disciples:

he saith unto them, why reason ye because ye have no bread? or imagine that I have given you this caution on that account; or are distressed because this is your case, as if you should be reduced to great difficulties, by reason of your forgetfulness and negligence:

perceive ye not yet, neither understand? the meaning of the parabolical expressions, which he had used them to; or his power in providing food for them, and supporting a great number of persons with very little food, of which they had some very late instances:

have ye your heart yet hardened? as after the first miracle; see Mark 6:52, for it might have been expected, that by a second miracle of the loaves, their understandings would have been more enlightened, and their faith increased, and that they would have relinquished their gross notions, their anxieties, doubts, and unbelief.