The resurrection is the only sign for the one asking.
"Then some of the scribes and Pharisees answered him, saying, “Teacher, we wish to see a sign from you.” But he answered them, “An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah" - Matthew 12:38-39
Ellicott's Commentary for English Readers There shall no sign be given to it.—The words seem at first to place our Lord’s miracles of healing outside the category of signs, and yet it was to these that He referred the messengers of the Baptist as proof that the Christ had indeed come (Matthew 11:5). They must, however, be interpreted by the context. One sign and only one, such as they demanded, should be given to those for whom the other notes of Messiahship were insufficient, and that should be the sign of the prophet Jonas.