Romans 16:17-18
<p class="default">  <b>17. Now I beseech you, brethren, mark them which cause divisions and offenses contrary to the doctrine which ye have learned; and avoid them.</b> 
 In Rome particularly this would have been the judaisers, who insisted that gentiles adhere to jewish tradition and law. 
 This is an example of the practice of avoiding fellowship with certain kinds of people, who are known by their actions to be sinful or divisive. 
 <b> 18. For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.</b>  </p>