John Chrysostom
Catena Aurea · Lukasevangelium 6
For if ye love them which love you, what thank have ye? for sinners also love those that love them. And if ye do good to them which do good to you, what thank have ye? for sinners also do even the same. And if ye lend to them of whom ye hope to receive, what thank have ye? for sinners also lend to sinners, to receive as much again. But love ye your enemies, and do good, and lend, hoping for nothing again; and your reward shall be great, and ye shall be the children of the Highest: for he is kind unto the unthankful and to the evil. Be ye therefore merciful, as your Father also is merciful.
(Hom. 58. in Gen.) Whereby thou wilt confer more upon thyself than him. For he is beloved by a fellow servant, but thou art made like unto God. But it is a mark of the greatest virtue when we embrace with kindness those who wish to do us harm. Hence it follows, And do good. For as water, when cast upon a lighted furnace, extinguishes it, so also reason joined with gentleness. But what water is to fire, such is lowliness and meekness to wrath; and as fire is not extinguished by fire, so neither is anger soothed by anger.