1 Corinthians 3:3
For ye are yet carnal: for whereas [there is] among you envying, and strife, and divisions, are ye not carnal, and walk as men?
Note 5 at 1Co 3:3: Paul cited envy, strife, and divisions as sure signs of carnality (see note 13 at Ro 8:6). As explained in notes 1-2 at 1Co 1:10, this is very different than the typical mindset of Christians today. The church today has focused its attention on the sins of immorality and has largely ignored things like unity among the believers.
The church at Corinth had the entire spectrum of sins present among its members. Paul dealt with the sins of immorality (1Co 7), but his emphasis was on the division among the believers. Jas 3:16 says, "For where envying and strife is, there is confusion and every evil work." Strife opens a door to every evil work that the Enemy wants to do in people's lives. Envy, strife, and division within the body of believers are even deadlier than the sins of immorality.