Augustine of Hippo
Catena Aurea · Johannesevangelium 14
I will not leave you comfortless: I will come to you. Yet a little while, and the world seeth me no more: but ye see me: because I live, ye shall live also. At that day ye shall know that I am in my Father, and ye in me, and I in you. He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him. Because I live, ye shall live also.
(Tract. lxxv. 5) He that hath them in mind, and keepeth them in life; he that hath them in words, and keepeth them in works; he that hath them by hearing, and keepeth them by doing; he that hath them by doing, and keepeth them by persevering, he it is that loveth Me. Love must be shewn by works, or it is a mere barren name.