2 John 1:5

Observe here, The duty required, together with the profession of the gospel; namely, to love in unity and peace, in amity and concord, one with another. This he calls. commandment, in the singular number, to intimate that in this one commandment all the rest are contained, and in keeping this we keep all: and he tells them, it is no new commandment, but an old one from the beginning; it is as old as Moses, yea, as old as Adam, being. part of the law of nature written in Adam's heart; yet, in some respects, love may be called a new commandment, because urged from new motives, and enforced by. new example; and because it is never to wax old, but to be always fresh in the memories, and found in the practice of Christ's disciples, to the end of the world: I write no new commandment, but what we had from the beginning, that we love one another.