What does Mark 8:11 mean?

The tenses of the words in the text suggest Jesus and the Pharisees have been arguing for some time before the Pharisees demand a sign. Matthew 16:1 says the Sadducees are there as well, unless this is a different day. "Signs" are miracles performed by God's prophets to validate their authority as spokesmen for God. The Pharisees know of the healings—including healing the blind and deaf—and exorcisms, but they want something more extreme, a literal "sign from heaven" that proves Jesus' authority is from God and not Satan (Mark 3:22–30). They want something like Elijah calling down fire from heaven to consume his sacrifice (1 Kings 18:36–38)Whatever the specific sign, they want something that proves He is God's Messiah who will lead them into freedom from Rome. Instead, Jesus scolds the Pharisees for understanding the weather but not the prophecies of the Old Testament (Matthew 16:2–3).

The request for a sign parallels Jesus' second temptation (Matthew 4:5–7). Satan had suggested Jesus throw Himself from the pinnacle of the temple. If He had done so, He would have proven His significance to God in front of the religious leaders. If history is any indication, the religious leaders would have found some way to give credit for the miracle to Satan (Mark 3:22), and the people would have tried to make Jesus king (John 6:15). Neither response would have served God's purpose. Jesus will face this temptation again while hanging on the cross (Mark 15:29–32).

We have people in our own lives with the same hardened heart. They find something in the Bible that takes away a freedom or authority and choose to reject Jesus because of it. Instead of submitting to all the evidence that Jesus is who He said He is, they close their ears, eyes, and understanding and come up with ridiculous arguments to justify their decision.