First John 3:11 says, "For this is the message which you heard from the beginning, that we should love one another."
Verse 23 says, "And this is His commandment, that we believe in the name of His Son Jesus Christ and love one another, even as He gave a commandment to us."
Loving one another is a commandment from God. God commands us to do two things: to believe in the name of His Son Jesus Christ and to love one another. We have already believed. Now we also should love. God gave us this love, and He also gave us the commandment to love. God first gave us this love and then He gave us the commandment to love one another. Today we must love one another according to God’s commandment. We must also love one another with the love which God has given us. We must exercise the love which God has put into us. We must apply it according to its nature. We should never quench it or hurt it.
First John 4:7-8 says, "Beloved, let us love one another, because love is of God, and everyone who loves has been begotten of God and knows God. He who does not love has not known God, because God is love."
We must love one another, because love is of God. Those who have love are begotten of God. Those who do not love have not known God because God Himself is love. When God begot us, He also begot love in us. We were without love, but today we have love. Today the love we possess is from God. God has begotten love in everyone who is born of God. God has given love to both you and others. This is why we can love one another.
Those who are begotten of God have received a life—a life which is God Himself. God is love; therefore, those who are begotten of God have such a love begotten within them. The life which we have received from God is a life of love. Everyone who is begotten of God has love in him, and everyone who has love in him spontaneously loves the brothers. It would be strange if we could not love one another. God gave every Christian a life of love. He also gave him the commandment of love based upon this life of love: "Let us love one another." God first gives us the love, and then He tells us to love. He first gives us a life of love, and then the commandment of love. We should bow our heads and say, "Thank You! God’s children can now love one another."
Now let us consider all the verses under this category in 1 John.
First John 2:9-11 says, "He who says he is in the light and yet hates his brother is in the darkness until now. He who loves his brother abides in the light, and there is no cause of stumbling in him; but he who hates his brother is in the darkness and walks in the darkness and does not know where he is going, because the darkness has blinded his eyes." Are you clear? Whether or not a man is a brother and whether or not he walks in the light and turns away from darkness are determined by whether or not he loves his brother.
If a person knows that you are a brother and yet he hates you in his heart, it proves that he is not a Christian. If he has seen five brothers and says, "I love four of them, but I hate one in my heart," it proves that he is not a brother. We must realize that we do not love a brother because he is lovable but because he is a brother. We love him because he is a brother. This is the only reason for us to love. If a person knows that you are a brother and are of the Lord yet still hates you, it proves that he has no life in him. Here it says, "He who hates his brother is in the darkness and walks in the darkness." He is in the darkness and he walks in the darkness. In other words, the Bible denies the possibility that anyone can hate his brothers; it does not accept this as a possibility at all. If you know that a person is a brother and yet hate him, you must say, "Lord, I am not walking in the light. I am in the darkness and am walking in the darkness."
(New Believers Series: Loving the Brothers #22, Chapter 1, by Watchman Nee)