What does the Bible say about heresies?

The Bible addresses heresies in 1 Corinthians 11:19, stating, 'For there must be also heresies among you, that they which are approved may be made manifest among you.' This highlights that heresies can serve a purpose in the church; they reveal those who hold to sound doctrine against those who deviate from it, ultimately demonstrating the true faith of believers. A crucial distinction exists between errors— which are mistaken beliefs that may not necessarily jeopardize one’s salvation—and heresies, which fundamentally reject core aspects of the faith, such as the nature of God, Christ’s divinity, or salvation through grace alone.