1 John 2:3-5 (NKJV)

3 "Now by this we know that we know Him, if we keep His commandments."
4 "He who says, "I know Him," and does not keep His commandments, is a liar, and the truth is not in him."
5 "But whoever keeps His word, truly the love of God is perfected in him. By this we know that we are in Him."