1 John 2:3

And now, in truth, it is time for me to cease from my instruction, and for you to listen to the Teacher. And He, receiving you who have been trained up in excellent discipline, will teach you the oracles. To noble purpose has the Church sung, and the Bridegroom also, the only Teacher, the good Counsel, of the good Father, the true Wisdom, the Sanctuary of knowledge. “And He is the propitiation for our sins,” as John says; Jesus, who heals both our body and soul, which are the proper man. “And not for our sins only, but also for the whole world. And by this 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 is the love of God perfected. Hereby know we that we are in Him. …

Ver. 3 . “And by this we know that we know Him, if we keep His commandments.” For the Gnostic [he who knows] also does the Works which pertain to the province of virtue. But he who performs the works is not necessarily also a Gnostic. For a man may be a doer of right works, and yet not a knower of the mysteries of science. Finally, knowing that some works are performed from fear of punishment, and some on account of the promise of reward, he shows the perfection of the man gifted with knowledge, who fulfils his works by love. Further, he adds, and says:

2. To these glorious beginnings of confession and the omens of a victorious warfare, has been added the maintenance of discipline, which I observed from the vigour of your letter that you lately sent to your colleagues joined with you to the Lord in confession, with anxious admonition, that the sacred precepts of the Gospel and the commandments of life once delivered to us should be kept with firm and rigid observance. Behold another lofty degree of your glory; behold, with confession, a double title to deserving well of God, to stand with a firm step, and to drive away in this struggle, by the strength of your faith, those who endeavour to make a breach in the Gospel, and bring impious hands to the work of undermining the Lord’s precepts: to have before afforded the indications of courage, and now to afford lessons of life. …

9. “And in this,” saith he, “we do know Him, if we keep His commandments.” What commandments? “He that saith, I know Him, and keepeth not His commandments, is a liar, and the truth is not in him.” But still thou askest, What commandments? “But whoso,” saith he, “keepeth His word, in him verily is the love of God perfected.” Let us see whether this same commandment be not called love. For we were asking, what commandments, and he saith, “But whoso keepeth His word, in him verily is the love of God perfected.” Mark the Gospel, whether this be not the commandment: “A new commandment,” saith the Lord, “give I unto you, that ye love one another. In this we know that we are in Him, if in Him we be perfected.” Perfected in love, he calls them: what is perfection of love? To love even enemies, and love them for this end, that they may be brethren. For not a carnal love ought ours to be. …