6 For mark, beloved brethren, how true it is what I say. When John was conceived, or rather when he was born, the Holy Spirit prophesied that this would be fulfilled in him: “And he shall be,” he said, “the forerunner of the Highest, in the spirit and power of Elias.” What signifies “in the spirit and power of Elias”? In the same Holy Spirit in the room of Elias. Wherefore in room of Elias? Because what Elias will be to the second, that John was to the first advent. Rightly therefore, speaking literally, did John reply. For the Lord spoke figuratively, “Elias, the same is John:” but he, as I have said, spoke literally when he said, “I am not Elias.” Neither did John speak falsely, nor did the Lord speak falsely; neither was the word of the herald nor of the Judge false, if only you understand. But who shall understand? He who shall have imitated the lowliness of the herald, and shall have acknowledged the loftiness of the Judge. For nothing was more lowly than the herald. My brethren, in nothing had John greater merit than in this humility, inasmuch as when he was able to deceive men, and to be thought Christ, and to have been received in the place of Christ (for so great were his grace and his excellency), nevertheless he openly confessed and said, “I am not the Christ.” “Are you Elias?” If he had said I am Elias, it would have been as if Christ were already coming in His second advent to judge, not in His first to be judged. As if saying, Elias is yet to come, “I am not,” said he, “Elias.” But give heed to the lowly One before whom John came, that you may not feel the lofty One before whom Elias came. For thus also did the Lord complete the saying: “John the Baptist is he which is to come.” He came as a figure of that in which Elias is to come in his own person. Then Elias will in his own proper person be Elias, now in similitude he was John. Now John in his own proper person is John, in similitude Elias. The two heralds gave to each other their similitudes, and kept their own proper persons; but the Judge is one Lord, whether preceded by this herald or by that.
7. “And they asked him, What then? Are you Elias? And he said, No. And they said unto him, Are you a prophet? And he answered, No! They said therefore unto him, Who are you? That we may give an answer to them that sent us. What do you say of yourself? He says, I am the voice of one crying in the wilderness.” That said Isaiah. This prophecy was fulfilled in John, “I am the voice of one crying in the wilderness.” Crying what? “Prepare ye the way of the Lord, make straight the paths of our God.” Would it not have seemed to you that a herald would have cried, “Go away, make room.” Instead of the herald's cry “Go away,” John says “Come.” The herald makes men stand back from the judge; to the Judge John calls. Yes, indeed, John calls men to the lowly One, that they may not experience what He will be as the exalted Judge. “I am the voice of one crying in the wilderness, Prepare ye the way of the Lord, as said the prophet Isaiah.” He did not say, I am John, I am Elias, I am a prophet. But what did he say? This I am called, “The voice of one crying in the wilderness, Prepare the way for the Lord: I am the prophecy itself.”
8. “And they which were sent were of the Pharisees,” that is, of the chief men among the Jews; “and they asked him and said unto him, Why do you baptize then, if you be not the Christ, nor Elias, nor a prophet?” As if it seemed to them audacity to baptize, as if they meant to inquire, in what character do you baptize? We ask whether you are the Christ; you say that you are not. We ask whether you perchance are His precursor, for we know that before the advent of Christ, Elias will come; you answer that you are not. We ask, if perchance you are some herald come long before, that is, a prophet, and hast received that power, and you say that you are not a prophet. And John was not a prophet; he was greater than a prophet. The Lord gave such testimony concerning him: “What went ye out into the wilderness to see? A reed shaken with the wind?” Of course implying that he was not shaken by the wind; because John was not such an one as is moved by the wind; for he who is moved by the wind is blown upon by every seductive blast. “But what went ye out for to see? A man clothed in soft raiment?” For John was clothed in rough garments; that is, his tunic was of camel's hair. “Behold, they who are clothed in soft raiment are in kings' houses.” You did not then go out to see a man clothed in soft raiment. “But what went ye out for to see? A prophet? Yea, I say unto you, one greater than a prophet is here;” for the prophets prophesied of Christ a long time before, John pointed Him out as present.
9. “Why do you baptize then, if you be not the Christ, nor Elias, nor a prophet? John answered them, saying, I baptize with water; but there stands One among you whom you know not.” For, very truly, He was not seen, being humble, and therefore was the lamp lighted. Observe how John gives place, who might have been accounted other than he was. “He it is who comes after me, who is made before me” (that is, as we have already said, is “preferred before me”), whose shoe's latchet I am not worthy to unloose. How greatly did he humble himself! And therefore he was greatly lifted up; for he that humbles himself shall be exalted. Hence, holy brethren, you ought to note that if John so humbled himself as to say, “I am not worthy to unloose His shoe-latchet,” what need they have to be humbled who say, “We baptize; what we give is ours, and what is ours is holy.” He said, Not I, but He; they say, We. John is not worthy to unloose His shoe's latchet; and if he had said he was worthy, how humble would he still have been! And if he had said he was worthy, and had spoken thus, “He came after me who is made before me, the latchet of whose shoe I am only worthy to unloose,” he would have greatly humbled himself. But when he says that he is not worthy even to do this, truly was he full of the Holy Spirit, who in such fashion as a servant acknowledged his Lord, and merited to be made a friend instead of a servant.
10. “These things were done in Bethany, beyond Jordan, where John was baptizing. The next day John saw Jesus coming unto him, and says, Behold the Lamb of God; behold Him who takes away the sin of the world!” Let no one so arrogate to himself as to say that he takes away the sin of the world. Give heed now to the proud men at whom John pointed the finger. The heretics were not yet born, but already were they pointed out; against them he then cried from the river, against whom he now cries from the Gospel. Jesus comes, and what says he? “Behold the Lamb of God!” If to be innocent is to be a lamb, then John was a lamb, for was not he innocent? But who is innocent? To what extent innocent? All come from that branch and shoot, concerning which David sings, even with groanings, “Behold, I was shapen in iniquity; and in sin did my mother conceive me.” Alone, then, was He, the Lamb who came, not so. For He was not conceived in iniquity, because not conceived of mortality; nor did His mother conceive Him in sin, whom the Virgin conceived, whom the Virgin brought forth; because by faith she conceived, and by faith received Him. Therefore, “Behold the Lamb of God.” He is not a branch derived from Adam: flesh only did he derive from Adam, Adam's sin He did not assume. He who took not upon Him sin from our lump, He it is who takes away our sin. “Behold the Lamb of God, who takes away the sin of the world!”
Source: Tractates on the Gospel of John (New Advent)