How is it that ye do not understand - We are not deficient in spiritual knowledge, because we have not had sufficient opportunities of acquainting ourselves with God; but because we did not improve the advantages we had. How deep and ruinous must our ignorance be, if God did not give line upon line, precept upon precept, here a little and there a little! They now perceived that he warned them against the superstition of the Pharisees, which produced hypocrisy, pride, envy, etc., and the false doctrine of the Sadducees, which denied the existence of a spiritual world, the immortality of the soul, the resurrection of the body, and the providence of God.

How is it that ye do not (f) understand that I (g) spake [it] not to you concerning bread, that ye should beware of the leaven of the Pharisees and of the Sadducees?
(f) A demand or question joined with wonder.
(g) "Spake" for commanded.

How is it that ye do not understand,.... That you should be so senseless and void of thought, after such instances, as to imagine, that I concerned myself about what bread you brought with you; one would think you could not but know,
that I spake it not to you concerning bread, taken in a literal sense; but must be thought to speak figuratively and mystically, and to have an higher sense and meaning, when I said to you,
that ye should beware of the leaven of the Pharisees, and of the Sadducees; how could you think that I had any regard to the leaven taken in a literal sense, the Pharisees and Sadducees approve or disapprove of?

How do ye not understand - Beside, do you not understand, that I did not mean bread, by the leaven of the Pharisees and Sadducees?