Origen — on Rev 5:6 (COMMENTARY ON THE GOSPEL OF JOHN 6.273-74)

“But if we examine the declaration about Jesus who is pointed out by John in the words, "This is the Lamb of God who takes away the sin of the world," from the standpoint of the dispensation itself of the bodily sojourn of the Son of God in the life of humankind, we will assume that the lamb is none other than his humanity. For he "was led as a sheep to the slaughter, and was dumb as a lamb before its shearer," saying, "I was as an innocent lamb being led to be sacrificed." This is why in the Apocalypse, too, a little lamb is seen "standing as though slain." This lamb, indeed, which was slain in accordance with certain secret reasons, has become the expiation of the whole world. In accordance with the Father's love for humanity, he also submitted to slaughter on behalf of the world, purchasing us with his own blood from him who bought us when we had sold ourselves to sins.”