Normally the Pharisees and Sadducees opposed each other, but in today’s passage they united in an effort to silence Jesus (v. 1). The Pharisees were the traditionalists of their day, and the Sadducees were the liberals. For the fourth time these religious leaders were asking for a sign more spectacular than healing.

In reply Jesus rebuked them for not being able to interpret the "signs of the times" that had already been given. They were able to predict the weather, but they could not or would not interpret the spiritual signs of the times (v. 2_3). They did not lack evidence; they lacked honesty and humility. Their demand for a sign revealed the sad condition of their hearts: they were evil and adulterous. Once before Jesus had spoken of the “sign of the prophet Jonah” (Matt. 12:39-41). As Jonah had spent three days in the belly of the great fish, so Jesus would spend three days “in the heart of the earth” before His resurrection.

As Jesus left these religious leaders, He warned His disciples against leaven (false doctrine) of the Pharisees and Sadducees (vv. 4-5). The disciples misunderstood Him and thought He was referring to the fact they had forgotten to bring along bread for the trip. They were more concerned about their own lack of food than what Jesus was trying to teach them (vv. 6-12). Because of this He rebuked them for their lack of faith in Him to provide. He reminded them of how He had multiplied the bread and fish for the 5,000 and the 4,000. Their "little faith" kept them from understanding His teaching and depending on His power to meet their needs