The greatest sign of all: The Resurrection.
Matthew 12:38 Then some of the scribes and Pharisees answered, saying, “Teacher, we want to see a sign from You.”
39 But He answered and said to them, “An evil and adulterous generation seeks after a sign, and no sign will be given to it except the sign of the prophet Jonah.
40 For as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth.
The scribes demand Jesus to show them a sign that He is the Christ. I love Jesus' answer, only those of an evil and adulterous heart seeks such in order to believe. They were scribes, copied Gods holy word, you know, all the prophecies that the LORD gave to help in this. But if one goes beyond what God has already given, that individual must look elsewhere. Spiritual adultery and all sorts of evil results. We have Gods word which is better than signs. Satan can decieve using signs. Jesus did say He would give one sign, the prophet Jonah. Which was a picture of resurrection. Look unto Jesus, the beginner & completor of your faith.