Charles Spurgeon 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)

Fundamentally, it was unbelief that clouded their understanding. Jesus may well say to doubters, “You do not understand.” Truly, nothing more effectively blunts spiritual perception than an overpowering anxiety for the bread which perisheth. When a doctrine is not understood, it may not always be the fault of the teacher. Very plain speaking is frequently misunderstood when the mind is absorbed in pressing needs.

It was sad to see apostles taking our Lord literally and failing to see the obvious parable of His words. How could “the leaven of the Pharisee” be a term used concerning bread?