1 John 2:4

He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him;

This is the negative of the same teaching given in 1 John 2:3. John's converse statement of the same principle here is blunt, powerful, and incapable of being misunderstood. It reminds one of Jesus' saying, "Not everyone that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father who is in heaven" (Matthew 7:21). All talk of knowing God, loving God, or even of "believing" or "having faith" is meaningless in the mouths of people who dishonor the commandments of the Lord through disobedience and failure to do the "work of faith." It is even more than meaningless; it is falsehood.