Deuteronomy 29:18 also makes this concept quite clear, warning of those whose heart turns away from the Lord, and making sure that there’s no root among you that produces such bitter poison. In other words, when a person no longer relies on God’s grace but themselves, they can become a root bearing bitter fruit…spreading doubt and disloyalty towards the Lord among fellow Believers. So we need to encourage one another to remain faithful… bring those who have turned away back to the Lord…but we also need to oppose any apostasy within the fellowship before there’s trouble and defilement.