1 St John 2:3-6

And by this we know that we have known him, if we keep his commandments. He who saith that he knoweth him, and keepeth not his commandments, is a liar, and the truth is not in him. But he that keepeth his word, in him in very deed the charity of God is perfected; and by this we know that we are in him. He that saith he abideth in him, ought himself also to walk, even as he walked.