11 How is it you do not understand that I did not speak to you concerning bread?--but to beware of the leaven of the Pharisees and Sadducees." 12 Then they understood that He did not tell them to beware of the leaven of bread, but of the doctrine of the Pharisees and Sadducees.
Matthew Henry's Commentary on Matthew 16:11-12
Commentary on Matthew 16:5-12
(Read Matthew 16:5-12)
Christ speaks of spiritual things under a similitude, and the disciples misunderstand him of carnal things. He took it ill that they should think him as thoughtful about bread as they were; that they should be so little acquainted with his way of preaching. Then understood they what he meant. Christ teaches by the Spirit of wisdom in the heart, opening the understanding to the Spirit of revelation in the word.