We ought to love our fellow believers in order to continue behaving like people living in the light.

1 John 2:7-11

7 Dear friends, I am not writing a new additional command to you. Instead, I am writing to you a command which was given to you when you first [MTY] believed in Christ. That command is part of the message that you have always heard. 8 Nevertheless, I can say that the command I am writing to you is a new command. It is new because what Christ did was new, and what you are doing is new, because you have been ceasing to conduct your lives in a morally impure manner and are now truly conducting your lives in a pure manner. That is like [MET] no longer living in darkness. Instead, it is like living where a brilliant light is already shining. 9 Those who claim that they are pure in every way, like people [MET] living in the light, but hate any of their fellow believers, are still behaving in an impure manner, like [MET] people who are continually living in darkness. 10 But those who love their fellow believers are continuing to conduct their lives like people who are living in the light. They are people who please God [LIT]. So you should love your fellow believers. 11 But those who hate any of their fellow believers are still conducting their lives in an impure way, like [MET] people who are living in darkness. They do not know that they will eventually destroy themselves eternally. They have become spiritually blind [PRS, MET], unaware of spiritual truth.