This is the message you heard from the beginning: We should love one another. (1 John 3:11)
John, the Apostle placed a lot of emphasis on this one command that the Saviour gave before he went to the cross for saving humanity from eternal death. This was what the master said.....
Love one another. As I have loved you, so you must love one another. (John 13:34)
And the apostle reminds us and all who read his epistle of the same.
And this is his command: to believe in the name of his Son, Jesus Christ, and to love one another as he commanded us. (1 John 3:23)
Repeatedly he exhorts his readers that love is very important, for, as he puts it, love comes from God.
Dear friends, let us love one another, for love comes from God. Everyone who loves has been born of God and knows God.(1 John 4:7)
Many believers fail in this matter because of various reasons. There are some who don't even love their own family members, leave alone others. Among the initial churches established by the apostles, there was often lack of love and we read in the epistles, several exhortations from them, to overcome this shortcoming and love each other genuinely.
The Apostle Paul wrote to the Colossians,
Therefore, as God's chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness and patience. Bear with each other and forgive whatever grievances you may have against one another. Forgive as the Lord forgave you.And over all these virtues put on love, which binds them all together in perfect unity. (Colossians 3:12-14)
Let us then humbly accept this command of the Lord and live as sons and daughters of the Most High.
No one has ever seen God; but if we love one another, God lives in us and his love is made complete in us. (1 John 4:12)