they swear by allah with their most solemn oaths that if a sign comes to them they will certainly believe in it. say signs are in allahs power alone. what will make you realize that even if those signs were to come they would still not believe?
وأقسموا بالله جهد أيمانهم لئن جاءتهم آية ليؤمنن بها قل إنما الآيات عند الله وما يشعركم أنها إذا جاءت لا يؤمنون