In ancient times, the corpse of a murdered person was attached to the murderer, allowing the body to decompose until the murderer was infected and died.
God's grace supports and fulfills us, but it does not mean 'once saved,always saved.' It is possible to fall from grace, as Israel's experience demonstrates.
Our outward works show what we believe, what we worship, and what we aspire to become. Apart from God, all human works activities are potentially destructive.