Augustine of Hippo — as excerpted in the Catena Aurea on John 15:8-11

“(Tract. lxxxii. 3. et seq.) Who doubts that love precedes the observance of the commandments? For who loves not, has not that whereby to keep the commandments. These words then do not declare whence love arises, but how it is shewn, that no one might deceive himself into thinking that he loved our Lord, when he did not keep His commandments. Though the words, Continue ye in My love, do not of themselves make it evident which love He means, ours to Him, or His to us, yet the preceding words do: I love you, He says: and then immediately after, Continue ye in My love. Continue ye in My love, then, is, continue in My grace: and, If ye keep My commandments, ye shall abide in My love, is, Your keeping of My commandments, will be evidence to you that ye abide in My love. It is not that we keep His commandments first, and that then He loves; but that He loves us, and then we keep His commandments. This is that grace, which is revealed to the humble, but hidden from the proud. But what means the next words, Even as I have kept My Father’s commandments, and abide in His love: i. e. the Father’s love, wherewith He loveth the Son. Must this grace, wherewith the Father loves the Son, be understood to be like the grace wherewith the Son loveth us? No; for whereas we are sons not by nature, but by grace, the Only Begotten is Son not by grace, but by nature. We must understand this then to refer to the manhood in the Son, even as the words themselves imply: As My Father hath loved Me, even so love I you. The grace of a Mediator is expressed here; and Christ is Mediator between God and man, not as God, but as man. This then we may say, that since human nature does not pertain to the nature of God, but does by grace pertain to the Person of the Son, grace also pertains to that Person; such grace as has nothing superior, nothing equal to it. For no merits on man’s part preceded the assumption of that nature.”