So he sleeps on. Jonah was the only human being on board who knew the true God. He was the only one who could lay hold of God for true help, and here he was dead to the world. It is hard to comprehend how he could sleep while the storm is raging. It shows how insensitive we can get.
Sin quickly hardens the heart.
A Callous is just skin that has lost its sensitivity. If you lose your callouses you will have tender feet or hands. Sin makes us spiritually insensitive. Our hearts are hardened. We do not respond to God.