'Commandment' in the Bible

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

Again, a new commandment write I unto you, which thing is true in him and in you; because the darkness is passing away, and the true light already shineth.

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

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