Can a genuine believer who is sinning still be happy?
No. A genuinely saved believer who goes out into sin cannot be happy; deep down he is miserable. He knows he is doing wrong, the Lord is dealing with him, and if fellow believers shun him, it comes home. Scripture admonishes believers not to fellowship with such people.
Les teaches that if a person has been genuinely saved, even though he goes out into sin, and if the Lord hasn’t yet taken him out as seen earlier in chapter 5, way down deep he’s miserable. He can’t be happy. Les says, 'Don’t tell me that a sinning believer can ever be happy.' They can’t be, because they know they are doing wrong, and the Lord is dealing with them, and then if fellow believers begin to shun them, it’s really going to come home. The purpose isn’t to be nasty, but God has a reason: if you have a person of your acquaintances who are believers, ostracize them for a while, but let them know why, because Scripture admonishes us not to have fellowship with those kind of people who claim to be believers. This is not about the world, but about believers. Paul says he has no authority to judge the lost world (verse 12). Les also points to Romans 8:6, showing this isn’t a little quirk of Scripture but a continuing doctrine throughout Paul’s letters on how to behave as a believer—practical, everyday living.