He answered and said to them, “An evil and adulterous generation seeks a sign, but no sign will be given to it except the sign of the prophet Jonah.”
Jesus’ answer was stern and direct. He labels the generation of the Pharisees and scribes as “evil and adulterous,” referring to their unbelief and to turning their loyalty away from God. The expression “adulterous generation” was used in the Old Testament to mean people’s unbelief, or the directing of their faithfulness away from God to other things or to idols. The Pharisees and scribes were demanding a special sign, but Jesus rejects their demand, stating that the only sign to be given by him will be “the sign of the prophet Jonah.” What that sign is will be spoken of in the next verse.