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.
41 The men of Nineveh will rise up in the judgment with this generation and condemn it, because they repented at the preaching of Jonah; and indeed a greater than Jonah is here.
42 The queen of the South will rise up in the judgment with this generation and condemn it, for she came from the ends of the earth to hear the wisdom of Solomon; and indeed a greater than Solomon is here.
adulterous (v.29) — unfaithful (to God)
great fish (v.40) = lit. “great sea monster” — In Jonah 1:17, the creature is referred to as a “great fish.”
Queen of the South (v.42) — Queen of Sheba (1 Kings 10)
They were not really prepared to receive a sign. If they had been, the casting out of the demons was in itself sufficient to have proved His cooperation with the Spirit of God, as He had declared. Thus when a sufficient sign had been given they had refused it by attempting to account for it in the most terrible way. Yet these men, already hardened against convincing signs, asked for one; and the asking was satirical, the asking of men who were not prepared to accept as sufficient any sign He could give, because of their personal hatred of Him. That is exactly what He meant when He declared in words of the sternest, “Ye generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh.” Their use of the word “Teacher” was in itself an insult, as they refused to accept Him or His teaching. — Morgan, page 133
While refusing a sign He promised a sign; and thus in the presence of their malicious hostility foretold the new opportunity which would be created for them by the carrying out to completeness of His divine work in the world. His purpose was that of saving and redeeming. Therefore He refused the sign they asked, which would have had no effect; and promised them the only sign that could by any means arrest and constrain them, that namely of His own resurrection from the dead after their malice had encompassed that death. The giving of that sign would afford them a new and final opportunity.
They knew how Jonah had been a sign to Nineveh in its sin by virtue of the fact that he had appeared in the city a preacher of Jehovah, after he had been cast out to death. That is the only possible solution of the words of the King here, for in that is the only parallel between Jonah and Jesus. — Morgan, page 134
Thus less enlightened people [Nineveh and the Queen of Sheba] had obeyed less enlightening preaching and teaching; and in that fact the patent condemnation of those to whom He spoke, and who were to receive His final sign was declared. — Morgan, page 135