Augustine of Hippo
Catena Aurea · Matthäusevangelium 5
Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you and persecute you; That ye may be the children of your Father which is in heaven: for He maketh His sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust. For if ye love them which love you, what reward have ye? do not even the Publicans the same? And if ye salute your brethren only, what do ye more than others? do not even the Publicans so? Be ye therefore perfect, even as your Father which is in heaven is perfect.
(de Doctr. Christ. i. 30.) That by the command, Thou shalt love thy neighbour, all mankind were intended, the Lord shewed in the parable of the man who was left half dead, which teaches us that our neighbour is every one who may happen at any time to stand in need of our offices of mercy; and this who does not see must be denied to none, when the Lord says, Do good to them that hate you.