Augustine of Hippo
Catena Aurea · Matthäusevangelium 22
But when the Pharisees had heard that he had put the Sadducees to silence, they were gathered together. Then one of them, which was a Lawyer, asked him a question, tempting him, and saying, Master, which is the great commandment in the Law? Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the Law and the Prophets.
(de Trin. viii. 6.) He that loves men ought to love them either because they are righteous, or that they may be righteous; and so also ought he to love himself either for that he is, or that he may be righteous. And thus without peril he may love his neighbour as himself.