Vidit Ioannes Iesum venientem ad se, et ait: Ecce Agnus Dei, ecce qui tollit peccatum mundi. (from the Gospel for the Commemoration of the Baptism of Our Lord Jesus Christ, John i, 29: "John saw Jesus coming to him, and he saith, Behold the Lamb of God, behold Him Who taketh 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. For He was not conceived in iniquity, because not conceived of mortality; nor did His mother conceive Him in sin, He whom the Virgin conceived, He 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!"
You know that certain men say sometimes, We take away sin from men, we who are holy; for if he be not holy who baptizes, how takes he away the sin of another, when he is a man himself full of sin? In opposition to these disputations, let us not speak our own words, let us read what John says: "Behold the Lamb of God; behold Him who takes away the sin of the world!" Let there not be presumptuous confidence of men upon men: let not the sparrow flee to the mountains, but let it trust in the Lord; and if it lift its eyes to the mountains, from whence comes aid to it, let it understand that its aid is from the Lord who made heaven and earth. ...
...was it needful for the Lord to be baptized? I instantly reply to any one who asks this question: Was it needful for the Lord to be born? Was it needful for the Lord to be crucified? Was it needful for the Lord to die? Was it needful for the Lord to be buried? If He undertook for us so great humiliation, might He not also receive baptism? And what profit was there that he received the baptism of a servant? That you might not disdain to receive the baptism of the Lord. ... the Lord, in order to invite such excellence to his baptism, that sins might be remitted, Himself came to the baptism of His servant; and although He had no sin to be remitted, nor was there anything in Him that needed to be washed, He received baptism from a servant
Saint Augustine
In Evangelium Ioannis - Tractatus IV
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Brother Alexis Bugnolo tells us of a new addition to his Franciscan Archive: My Life with Mary, a beautiful Marian prayer booklet, freely available here.