'Commandment' in the Bible

Beloved, 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 message which you have heard [before from us].

On the other hand, I am writing a new commandment to you, which is true and realized in Christ and in you, because the darkness [of moral blindness] is clearing away and the true Light [the revelation of God in Christ] is already shining.