Augustine of Hippo
Catena Aurea · Johannesevangelium 13
Little children, yet a little while I am with you. Ye shall seek me: and as I said unto the Jews, Whither I go, ye cannot come; so now I say to you. A new commandment I give unto you, That ye love one another; as I have loved you, that ye also love one another. By this shall all men know that ye are my disciples, if ye have love one to another.
(Tr. lxv. 1) And now He teaches them how to fit themselves to follow Him: A new commandment I give unto you, that ye love one another. (Levit. 19:18) But does not the old law say, Thou shall love thy neighbour as thyself? Why then does He call it a new commandment? Is it because it strips us of the old man, and puts on us the new? That it renews the hearer, or rather the doer of it? Love does do this; but it is that love which our Lord distinguishes from the carnal affection: As I have loved you, that ye also love one another. Not the love with which men love one another, but that of the children of the Most High God, who would be brethren of His only-begotten Son, and therefore love one another with that love with which He loved them, and would lead them to the fulfilment of their desires.