What is the context?
Some scribes and Pharisees ask Jesus for a sign after the healings and confrontation already described. He treats this demand as the response of a wicked and adulterous generation. The problem is not a lack of anything to consider; His works and their meaning have already been before them.
The Greek verb for demanding a sign is ἐπιζητέω, epizēteō (eh-pee-zay-TEH-oh), to seek after or demand. Thayer's entry lists this verse under demanding or clamoring for a sign. Jesus directs them to the sign of Jonah rather than letting a continuing demand for proof determine His mission.
He connects Jonah's three days and nights in the fish with the Son of Man's time in the heart of the earth. Jonah 1:17–2:10 describes the prophet's descent into distress and deliverance; the prayer and release continue in chapter 2. Jesus' own coming death and resurrection give the comparison its greater meaning.
The Ninevites and the Queen of the South provide two more comparisons. Jonah 3:1–10 describes repentance at Jonah's preaching; 1 Kings 10:1–9 describes the queen coming to hear Solomon and recognizing the wisdom God gave him. These outsiders responded to messengers less great than the One now present. Their response exposes the failure to receive Him.
How is this passage commonly understood?
Christians commonly understand Jonah's experience here as pointing toward Jesus' death, burial, and resurrection, while the Ninevites and the queen illustrate responsibility to respond to God's revelation. Wesley on Matthew 12:39–42 reads Jonah as a picture of Christ and understands the three-day wording as including parts of days. The Catholic Catechism, 624, emphasizes the reality of Jesus' death and His time in the tomb before the resurrection. The central connection is His passage through death into life.
Where does this fit in God's plan?
This is a connection Jesus Himself makes: Jonah's experience points ahead to what the Son of Man will undergo. The parallel does not make the prophet and Savior equal. Jesus is greater than Jonah, just as He is greater than Solomon; His own victory will stand at the center of the message.
1 Corinthians 15:1–8 presents that center directly: Christ dies for sins, is buried, is raised on the third day according to the Scriptures, and appears to witnesses. The sign reaches beyond an impressive event to God's saving work. The call is to receive the risen Savior and the good news about Him.
What is our position?
Should We Seek Signs From God? reads this as a warning against demanding another sign while resisting what God has already revealed. These leaders have already seen Jesus' works; the study distinguishes their demand from sincerely seeking to understand and obey Him.