And a generation died off. There is a carnal generation in each of our lives that needs to die off. It occurs when you have eaten enough manna. Notice the wording. They ate manna until they came to Canaan.
Manna speaks of the truths of the cross.
He referred to His death on the cross. We need to feast on the truths of the cross until we come to spiritual maturity. Learn about and be made fully acquainted with the work Christ did to us in our salvation. Until the doubting falls away. Until that fleshly generation of unbelief and all the bad traits of carnality fall away dead.