Gregory the Great
Catena Aurea · Johannesevangelium 15
This is my commandment, That ye love one another, as I have loved you. Greater love hath no man than this, that a man lay down his life for his friends. Ye are my friends, if ye do whatsoever I command you. Henceforth I call you not servants; for the servant knoweth not what his Lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you. Ye have not chosen me, but I have chosen you, and ordained you, that ye should go and bring forth fruit, and that your fruit should remain: that whatsoever ye shall ask of the Father in my name, he may give it you.
(Hom. xxvii.) The highest, the only proof of love, is to love our adversary; as did the Truth Himself, who while He suffered on the cross, shewed His love for His persecutors: Father, forgive them, for they know not what they do. (Luke 23:34) Of which love the consummation is given in the next words:Greater love hath no man than this, that a man lay down his life for his friends. Our Lord came to die for His enemies, but He says that He is going to lay down His life for His friends, to shew us that by loving, we are able to 1 gain over our enemies, so that they who persecute us are by anticipation our friends.