Augustine Tractates of John 27:9; 29.6; 40.9

27.9. And now addressing the few that remained: Then said Jesus to the twelve (namely, those twelve who remained), Will ye also, said He, go away? Not even Judas departed. But it was already manifest to the Lord why he remained: to us he was made manifest afterwards. Peter answered in behalf of all, one for many, unity for the collective whole: Then Simon Peter answered Him, Lord, to whom shall we go? You drive us from You; give us Your other self. To whom shall we go? If we abandon You, to whom shall we go? You have the words of eternal life. See how Peter, by the gift of God and the renewal of the Holy Spirit, understood Him. How other than because he believed? You have the words of eternal life. For You have eternal life in the ministration of Your body and blood. And we have believed and have known. Not have known and believed, but believed and known. For we believed in order to know; for if we wanted to know first, and then to believe, we should not be able either to know or to believe. What have we believed and known? That You are Christ, the Son of God; that is, that You are that very eternal life, and that You give in Your flesh and blood only that which You are.

29.6 If we have understood this, thanks be to God; but if any has not sufficiently understood, man has done as far as he could: as for the rest, let him see whence he may hope to understand. As laborers outside, we can plant and water; but it is of God to give the increase. My doctrine, says He, is not mine, but His that sent me. Let him who says he has not yet understood hear counsel. For since it was a great and profound matter that had been spoken, the Lord Christ Himself did certainly see that all would not understand this so profound a matter, and He gave counsel in the sequel. Do you wish to understand? Believe. For God has said by the prophet: Unless you believe, you shall not understand. Isaiah 7:9 To the same purpose what the Lord here also added as He went on— If any man is willing to do His will, he shall know concerning the doctrine, whether it be of God, or whether I speak from myself. What is the meaning of this, If any man be willing to do His will? But I had said, if any man believe; and I gave this counsel: If you have not understood, said I, believe. For understanding is the reward of faith. Therefore do not seek to understand in order to believe, but believe that you may understand; since, except ye believe, you shall not understand. Therefore when I would counsel the obedience of believing toward the possibility of understanding, and say that our Lord Jesus Christ has added this very thing in the following sentence, we find Him to have said, If any man be willing to do His will, he shall know of the doctrine. What is he shall know? It is the same thing as he shall understand. But what is If any man be willing to do His will? It is the same thing as to believe. All men indeed perceive that shall know is the same thing as shall understand: but that the saying, If any man be willing to do His will, refers to believing, all do not perceive; to perceive this more accurately, we need the Lord Himself for expounder, to show us whether the doing of the Father’s will does in reality refer to believing. But who does not know that this is to do the will of God, to work the work of God; that is, to work that work which is pleasing to Him? But the Lord Himself says openly in another place: This is the work of God, that you believe in Him whom He has sent. John 6:29That ye believe in Him, not, that you believe Him. But if you believe on Him, you believe Him; yet he that believes Him does not necessarily believe on Him. For even the devils believed Him, but they did not believe in Him. Again, moreover, of His apostles we can say, we believePaul; but not, we believe in Paul: we believe Peter; but not, we believe in Peter. For, to him that believes in Him that justifies the ungodly, his faith is counted unto him for righteousness.Romans 4:5 What then is to believe in Him? By believing to love Him, by believing to esteem highly, by believing to go into Him and to be incorporated in His members. It is faith itself then that God exacts from us: and He finds not that which He exacts, unless He has bestowed what He may find. What faith, but that which the apostle has most amply defined in another place, saying, Neither circumcision avails anything, nor uncircumcision, but faith that works by love? Galatians 5:6 Not any faith of what kind soever, but faith that works by love: let this faith be in you, and you shall understand concerning the doctrine. What indeed shall you understand? That this doctrine is not mine, but His that sent me; that is, you shall understand that Christ the Son of God, who is the doctrine of the Father, is not from Himself, but is the Son of the Father.

40.9. What, brethren, does He promise believers? And you shall know the truth. Why so? Had they not come to such knowledge when the Lord was speaking? If they had not, how did they believe? They believed, not because they knew, but that they might come to know. For we believe in order that we may know, we do not know in order that we may believe. For what we shall yet know, neither eye has seen, nor ear heard, nor has it entered the heart of man. For what is faith, but believing what you see not? Faith then is to believe what you see not; truth, to see what you have believed, as He Himself says in a certain place. The Lord then walked on earth, first of all, for the creation of faith. He was man, He was made in a low condition. He was seen by all, but not by all was He known. By many was He rejected, by the multitude was He slain, by few was He mourned; and yet even by those who mourned Him, His true being was still unrecognized. All this is the beginning as it were of faith’s lineaments and future up-building. As the Lord, referring thereto, says in a certain place, He that loves me keeps my commandments; and he that loves me shall be loved of my Father, and I will love him, and will manifest myself to him. They certainly already saw the person to whom they were listening; and yet to them, if they loved Him, does He give it as a promise that they should see Him. So also here, You shall know the truth. How so? Is that not the truth which You have been speaking? The truth it is, but as yet it is only believed, not beheld. If you abide in that which is believed, you shall attain to that which is seen. Hence John himself, the holy evangelist, says in his epistle, Dearly beloved, we are the sons of God; but it is not yet apparent what we shall be. We are so already, and something we shall be. What more shall we be than we are? Listen: It is not yet apparent what we shall be: [but] we know that, when He shall appear, we shall be like Him. How? For we shall see Him as He is. 1 John 3:2 A great promise, but the reward of faith. You seek the reward; then let the work precede. If you believe, ask for the reward of faith; but if you believe not, with what face can you seek the reward of faith? If then ye continue in my word, you shall be my disciples indeed, that you may behold the very truth as it is, not through sounding words, but in dazzling light, wherewith He shall satisfy us: as we read in the psalm, The light of Your countenance is impressed upon us. We are God’s money: we have wandered away as coin from the treasury. The impression that was stamped upon us has been rubbed out by our wandering. He has come to refashion, for He it was that fashioned us at first; and He is Himself asking for His money, as Cæsar for his. Therefore He says, Render unto Cæsar the things that are Cæsar’s, and unto God the things that are God’s: Matthew 22:21 to Cæsar his money, to God yourselves. And then shall the truth be reproduced in us.