What does Matthew 16:2 mean?

A group of Jewish religious leaders, composed of both Pharisees and Sadducees, have approached Jesus to ask for a sign from heaven. Their request implies a demand for supernatural evidence that He is truly the Messiah. In other words, they are asking Him to perform a miracle on demand to earn their belief. Matthew writes they are testing Jesus, likely trying to catch Him doing something they can use to discredit Him; they are not sincerely validating His authority.

This is not the first time some Pharisees have asked Jesus for a sign. Matthew records Jesus' response to the same request in chapter 12. There He said that a "evil and adulterous generation asks for a sign" (Matthew 12:39). In the following verses, though, Jesus points out that these men have already missed the signs they have been given (John 5:39–40).

He begins by showing these men are capable of distinguishing basic signs of the weather. These words parallel a common expression in English: "Red sky in the morning, sailor take warning; red sky at night, sailor's delight." Jesus' point is that common sense and experience lead to some obvious conclusions. One does not need excessive information to understand what's clearly happening. Jesus is not describing superstition or supernatural events, only the common patterns of clouds and storms observable by all people.

Those who can read such signs, and who have seen Jesus' other miracles, have no reason to need even more proof.