Mk 8:11-13
11The Pharisees came forward and began to argue with [Jesus], seeking from him a sign from heaven to test him. 12He sighed from the depth of his spirit and said, “Why does this generation seek a sign? Amen, I say to you, no sign will be given to this generation.” 13Then he left them, got into the boat again, and went off to the other shore.
REQUEST FOR A SIGN: A sign in the Old Testament and Jewish literature signifies a token which guarantees the truthfulness of an utterance or the legitimacy of an action. The words of the prophets which could not be verified were frequently accompanied by a sign which authenticated the prophecy. In that context, a sign is a further prophecy that is to be fulfilled within a short period of time.
A well-known Old Testament sign is the birth of a male child in the household of King Ahaz which signifies that Isaiah’s prophecy about the deliverance of Jerusalem will soon come to pass. Hence, the child will be called “Immanuel” because it is a sign that “God is with us (his people)” and he will deliver them from his enemies (cf Is 7:14).
Because miracles are effective and extraordinary, they occupy a privileged place among the divine signs, but they are not always “signs” pointing to God’s saving action. Jesus does miracles designated as signs of the coming of the Kingdom, but they are not considered to be signs by the Pharisees. When they see with their very eyes Jesus’ mighty deeds, they conclude that these are of demonic agency and that Jesus is in league with Beelzebul, the prince of demons. That is why in today’s Gospel they seek a sign from heaven. They demand that Jesus demonstrate the legitimacy of his actions. Jesus is thoroughly aware of the hostility and unbelief of the Pharisees who are opposed to the revelation of God’s grace in him. In their case, he absolutely refuses the demand for a sign.