William Burkitt on Luke 6:31

Here our Saviour lays down a most excellent rule of life, for all his disciples and followers to walk by, namely, always to do as we would be done by. The golden rule of justice and equity in all our dealings with men is this, To do as we would be done unto. It is a full rule, a clear rule, a most just and equitable rule, which the light of nature, and the law of Christ, binds upon us.

This is the law and the prophets; Matt 7:12 That is, the sum of the Old Testament, and the substance of the second table. The whole of the law is this; to love God above ourselves, and to love our neighbors as ourselves.