(John 4:48) Then said YaHshua unto him, "Except you see signs and wonders, you will not believe".
(Mat 24:24) For there shall arise false Christs, and false prophets, and shall show great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
(1Co 4:6) Now, brothers, I have applied these things to myself and Apollos for your benefit, so that you may learn from us the meaning of the saying, "Do not go beyond what is written." Then you will not take pride in one man over against another.
What? No signs? No signs given but one, the "sign" of Jonas and what would that be? That our Lord would be in the grave for three days and three nights, just like Jona was in the belly of the great fish had been. Notice, this is not just to that generaation of Jews, our Lord makes a blanket statement that would cover any generation seeking after such things, and He repeats this in Matthew 16:4.(Mat 12:39) But He answered and said unto them, "An evil and adulterous generation seekes after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas: ..."
(2Th 2:8-10) And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of His mouth, and shall destroy with the brightness of His coming: Even him, whose coming is after the working of Satan with all power and signs and lying wonders, And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.