Augustine of Hippo
Catena Aurea · Johannesevangelium 15
These things I command you, that ye love one another. If the world hate you, ye know that it hated me before it hated you. If ye were of the world, the world would love his own: but because ye are not of the world, but I have chosen you out of the world, therefore the world hateth you. Remember the word that I said unto you, The servant is not greater than his lord. If they have persecuted me, they will also persecute you; if they have kept my saying, they will keep yours also. But all these things will they do unto you for my name’s sake, because they know not him that sent me.
(Tract. lxxxvii. 1) Our Lord had said, I have ordained that ye should walk, and bring forth fruit. Love is this fruit. Wherefore He proceeds: These things I command you, that ye love one another. (Gal. 5:22) Hence the Apostle saith: The fruit of the Spirit is love; and enumerates all other graces as springing from this source. Well then doth our Lord commend love, as if it were the only thing commanded: seeing that without it nothing can profit, with it nothing be wanting, whereby a man is made good.