To disobey God is not a minor thing. We see this in the disobedience of Adam and Eve. We are not God’s equal. When one considers all that Jesus suffered to atone for sin, it ought to give us pause. He is not only showing us something of the magnitude of infinite love, He is also showing us what an offense sin is against an infinitely good God.
Being killed by becoming a pillar of salt is not the ultimate punishment. Death comes to us all. The ultimate punishment is to choose ourselves over God for all eternity—which what hell is.
Onan disobeyed God in failing to put his duty to the family and nation before his own self-interest. The God-given Mosaic ‘levirate’ law required that the child which would have been conceived would have been considered the child of his dead brother and Onan chose to disobey it.
We live in a culture that disdains and trivializes the virtue of obedience. To obey lawful authority, of course, is to acknowledge and acquiesce to a right that is not ours. This can offend our pride and our desire for un-restrained dominance over our lives. But God does a much better job of being God than we ever could. To obey Him is to be fully ourselves.
There is no easy way to learn this. We all learn it the hard way. But learn it we must.
Fr. Vincent Serpa, O.P.