apostatize

verb

1. To give up or renounce one's position or belief.

   “Q. 15. May not a church so far apostatize by the neglect of discipline, as to cease to be a church of Christ, and become a synagogue of Satan? A. Yes. This has sometimes happened.”

   “Soft enticements of domestic life too often draw him from the ascetic trail; a monk who apostatizes to the world at times.”