Matthew 12:38

σημεῖον : what kind of a sign? They thought the cure of demoniacs a sign from hell. Elsewhere we read of their asking a sign from heaven (Matthew 16:1). From what quarter was the sign now asked to come from? Perhaps those who made the demand had no idea; neither knew nor cared. Their question really meant: these signs won't do; if you want us to believe in you you must do something else than cast out devils. The apparent respect and earnestness of the request are feigned: “teacher, we desire from you (emphatic position) to see a sign”. It reminds one of the mock homage of the soldiers at the Passion (Matthew 27:27-31).