What does the sign of Jonah signify?

In Mark 8:12, Jesus mentions that no sign will be given to an evil generation except for the sign of Jonah. This refers to Jonah’s three days in the belly of the fish, paralleling Jesus’ three days in the tomb. Just as Jonah was a sign to the Ninevites, Jesus’ death and resurrection become the ultimate sign of His messianic authority and God’s redemptive plan. It emphasizes that faith in Christ's resurrection is what ultimately points to His identity and the hope of salvation for all who believe.