William Burkitt on Luke 11:29

The sign which the Pharisees here desired of our Saviour, was a miracle wrought by him. Now our Saviour, though he was very ready to work miracles to encourage and confirm his hearers' faith, yet not to satisfy the unbelieving Pharisees' curiosity: and accordingly he tells them, they should have no other sign than that of his resurrection, which Jonas was a type of.

Next he threatens them for their obstinacy and infidelity, which he aggravates from the example of the queen of the south, and the men of Nineveh.

From thence learn, that the sins of infidelity and impenitency are exceedingly heightened, and their guilt aggravated, from the means afforded by God to bring men to faith and obedience. The sin of the Pharisees was infinitely greater in rejecting the evidence of Christ's miracles, than the sin of the Ninevites would have been in refusing to hearken to Jonas's ministry; therefore the Ninevites shall condemn the Pharisees.