What does the Bible say about going back to old beliefs?

In the book of John, particularly John 6:67, Jesus poses a question to His disciples after many had left Him: 'Will ye also go away?' This illustrates that true believers, those who have been granted faith by the Father, can never genuinely turn away from Christ. Similarly, the story of Micah in Judges 17 serves as a sobering reminder that those who adopt idolatrous practices do so in rebellion against God's commandments. A true conversion leads to a steadfast commitment to Christ, and as 1 John 2:19 indicates, if someone leaves the faith, they never truly belonged to it in the first place.