The one saying “I know him” and keeps not his commands is a liar, and the truth is not in him. Now, whoever keeps his word, truly in this person the love of God is matured in knowledge, because existing in him. The one saying he abides in God ought to walk just as Jesus walk - 1 John 2:3-6 John relates keeping his commands to keeping the words of Jesus, not to be confused with commandments, handwritings, decrees, rules and regulations, elemental principles that have no power to overcome the desires of the flesh so that one can keep his words. In a place of maturity one finds that his words or commands are not burdensome. And this is how we know the love of God is fulfilled or completed or matured, when we find keeping his words are not burdensome. Maturity comes through knowledge of the Son, the words of Jesus increase our faith, and faith works through love thus we know God's love is matured in us when we have faith, when we are fully convinced of his words and promises. ...
When we bear fruit, after being deeply rooted, and growing up truth in love, the love of God is fulfilled.