Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them. Romans 16:17 (KJV)
The Apostle Paul concludes his letter to the Romans, with this warning, ‘beware of false teachers.’ It appears Paul was constantly battling with false teachers who followed his steps and perverted the truth of the gospel. You can see this in some of his writings to the church at Corinth, where false apostles posing as servants of righteousness caused much damage (2 Cor. 11:3-15). As he thought of his many dear friends in Rome, he didn’t want them to be led astray. He had heard that they were doing well in the Lord (16:19a), but the present is no guarantee for the future. His love for the church prompted him to insert this warning against the dangers of false teachers.
By the same token mark and avoid people who claim to be servants of God yet they are serving the devil. Believers need to be on guard against false teaching. False teachers are usually nice and likeable. They will tell you what you want to hear even at the expense of the true gospel.