Though Christ is always ready to hear and answer holy desires and prayers, yet those who ask amiss, ask and have not. Signs were granted to those who desired them to confirm their faith, as Abraham and Gideon; but denied to those who demanded them to excuse their unbelief.
The resurrection of Christ from the dead by his own power, called here the sign of the prophet Jonah, was the great proof of Christ's being the Messiah. As Jonah was three days and three nights in the whale, and then came out again alive, thus Christ would be so long in the grave, and then rise again.
The Ninevites would shame the Jews for not repenting; the queen of Sheba, for not believing in Christ. And we have no such cares to hinder us, we come not to Christ upon such uncertainties. This parable represents the case of the Jewish church and nation.
It is also applicable to all those who hear the word of God, and are in part reformed, but not truly converted. The unclean spirit leaves for a time, but when he returns, he finds Christ is not there to shut him out; the heart is swept by outward reformation, but garnished by preparation to comply with evil suggestions, and the man becomes a more decided enemy of the truth.
Every heart is the residence of unclean spirits, except those which are temples of the Holy Ghost, by faith in Christ.