John Gill Commentary Matthew 16:11

"How is it that ye do not perceive that I spake not to you concerning bread? But beware of the leaven of the Pharisees and Sadducees." — Matthew 16:11 (ASV)

How is it that you 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 spoke 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 you 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?