I am amazed that you are so quickly deserting Him who called you by the grace of Christ, for a different gospel; which is really not another; only there are some who are disturbing you and want to distort the gospel of Christ.  But even if we, or an angel from heaven, should preach to you a gospel contrary to what we have preached to you, he is to be accursed!  As we have said before, so I say again now, if any man is preaching to you a gospel contrary to what you received, he is to be accursed! Galatians 1:6-9

This is a strong message. If any man is preaching a gospel contrary . . . So, how do we know what is preached that is contrary? We must practice discernment. Line up what is being said by man by what is said in scripture.

1 Thessalonians 5:21-22 says: But examine everything carefully; hold fast to that which is good; abstain from every form of evil.

1 John 4:1 tells us: Do not believe every spirit, but test the spirits to see whether they are from God; because many false prophets have gone out into the world.

His word is a plumb line of truth. John 17:17 – Sanctify them in the truth; Your word is truth.