'Commandment' in the Bible

Dear friends, I am not writing a new commandment to you, but an old commandment which you have had from the beginning. The old commandment is the word that you have already heard.

On the other hand, I am writing a new commandment to you which is true in him and in you, because the darkness is passing away and the true light is already shining.

Now this is his commandment: that we believe in the name of his Son Jesus Christ and love one another, just as he gave us the commandment.

And the commandment we have from him is this: that the one who loves God should love his fellow Christian too.