The leaders wanted proof on their own terms, and Jesus exposed the problem. They were skilled at reading the weather from the color of the sky, but they could not, or would not, read what God was doing in front of them. Barnes says their request was a trap: they were "feigning a desire to see evidence that he was the Messiah," hoping to see Him try a miracle and fail. Gill says they came "with no sincere view to be taught by him." So Jesus' question presses them: if you can read the sky, why can you not read the times?

The leaders' answer is not recorded. Jesus went on: "A wicked and adulterous generation seeketh after a sign; and there shall no sign be given unto it, but the sign of the prophet Jonas." Then "he left them, and departed" (Matthew 16:4). Barnes points readers to Matthew 12:38-40, where Jesus explained that sign: "as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth" (Matthew 12:40).

Barnes explains the weather sign: a red, "lowering" sky in the morning meant threatening clouds lit by the rising sun, and "This, in Judea, was a sign of a tempest." The KJV word "lowring" translates stugnazō, which Thayer defines as to be sad or to have a gloomy look. The same word describes the rich young man who "was sad at that saying" (Mark 10:22).

The Textus Receptus, the Greek text behind the KJV, includes this verse in full, with the address "hypocrites." Some ancient manuscripts leave out the weather sayings, which is why an ESV footnote at Matthew 16:2 says some manuscripts omit the words from there to the end of Matthew 16:3, and some Greek editions omit "hypocrites." Luke records a similar saying (Luke 12:54-56).

God had already given many signs. Just before this, Jesus healed the lame, the blind, the dumb, and the maimed, and fed four thousand men (Matthew 15:30-38). Barnes summarizes Jesus' point: "My miracles, and the state of affairs in Judea, are an indication by which you should judge." Gill lists among those signs "the departure of the sceptre from Judah," "the ending of Daniel's weeks," and "the various miracles wrought by Christ."

The problem was not lack of evidence but an unwilling heart. Matthew Henry says, "It is great hypocrisy, when we slight the signs of God's ordaining, to seek for signs of our own devising." Jesus would give one more sign, the sign of Jonah, pointing to His death and resurrection. Jesus would not give a sign on demand to those who had already refused what God had shown them (Matthew 16:4).