1 John 2:3-7

And hereby we know that we know him, if we keep his commandments. He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him; but whoso keepeth his word, in him verily hath the love of God been perfected. Hereby we know that we are in him: he that saith he abideth in him ought himself also to walk even as he walked. Beloved, no new commandment write I unto you, but an old commandment which ye had from the beginning: the old commandment is the word which ye heard.