What´s Sound Doctrine?

What is sound doctrine? Good question. The Bible provides the answers. Right off the bat, there are two extremes to avoid. The first extreme is to seek justification by the Law. Apostle Paul addressed this issue in several of his letters to believers in the New Testament (Book of Romans & Galatians). The second extreme is turning the grace of God into a license for sin (Jude 1:4).
In 1 John and 2 John, the writer highlighted a group of people that later came to be known as the Gnostics for their erroneous belief that Christ has not come in human form of a man because all flesh is evil. Moreover, they believed that it is alright to believers in Christ to continue to sin. The spirit is saved and all flesh will be destroyed at the end.
Clearly,