'Commandment' in the Bible

Brethren, I write no new commandment unto you, but an old commandment which ye had from the beginning. The old commandment is the word which ye have heard from the beginning.

Again, a new commandment I write unto you, which thing is true in him and in you: because the darkness is past, and the true light now shineth.

And this is his commandment, That we should believe on the name of his Son Jesus Christ, and love one another, as he gave us commandment.

And this commandment have we from him, That he who loveth God love his brother also.