Deuteronomy 32:15 But Jeshurun waxed fat, and kicked: thou are waxen fat, thou art grown thick, thou art covered with fatness; then he forsook God which made him, and lightly esteemed the Rock of his salvation.
Jeshurun is like a pet name for the children of Israel, and by extension, for all the children of God. He is speaking about us. He is telling us who we really are and what we are doing in response to God’s salvation from the kingdom of darkness and death and His salvation into the Kingdom of light and life.
After we have grown prosperous, smug, and secure by grace, we forsook the God who made us new and gave us a good life. To forsake is to abandon, leave, forget, ignore, and even reject God. To esteem lightly is to scoff, scorn, spurn, even reject our Rock of salvation. We forget God and spurn salvation every time we sin. If we had God on our minds and remembered His love, we wouldn’t have sinned in that moment.
We don’t usually think of every little sin as being so serious as forsaking God, but that’s what God sees. The response of thanking and praising, serving and obeying Him is meant to be all the time, in every circumstance. But we forget whose we are. Daily repentance and returning are necessary. And the Lord is always there to receive us. He doesn’t forget. He will never, never forsake us.