John 6:49
4 Awful in truth are the Mysteries of the Church, awful in truth is the Altar. A fountain went up out of Paradise sending forth material rivers, from this table springs up a fountain which sends forth rivers spiritual. By the side of this fountain are planted not fruitless willows, but trees reaching even to heaven, bearing fruit ever timely and undecaying. If any be scorched with heat, let him come to the side of this fountain and cool his burning. For it quenches drought, and comforts all things that are burnt up, not by the sun, but by the fiery darts. For it has its beginning from above, and its source is there, whence also its water flows. Many are the streams of that fountain which the Comforter sends forth, and the Son is the Mediator, not holding mattock to clear the way, but opening our minds. This fountain is a fountain of light, spouting forth rays of truth. By it stand the Powers on high looking upon the beauty of its streams, because they more clearly perceive the power of the Things set forth, and the flashings unapproachable. For as when gold is being molten if one should (were it possible) dip in it his hand or his tongue, he would immediately render them golden; thus, but in much greater degree, does what here is set forth work upon the soul. Fiercer than fire the river boils up, yet burns not, but only baptizes that on which it lays hold. This blood was ever typified of old in the altars and sacrifices of righteous men, This is the price of the world, by This Christ purchased to Himself the Church, by This He has adorned Her all. For as a man buying servants gives gold for them, and again when he desires to deck them out does this also with gold; so Christ has purchased us with His blood, and adorned us with His blood. They who share this blood stand with Angels and Archangels and the Powers that are above, clothed in Christ's own kingly robe, and having the armor of the Spirit. Nay, I have not as yet said any great thing: they are clothed with the King Himself.
Now as this is a great and wonderful thing, so if you approach it with pureness, you approach for salvation; but if with an evil conscience, for punishment and vengeance. “For,” It says, “he that eats and drinks unworthily” of the Lord, “eats and drinks judgment to himself”; since if they who defile the kingly purple are punished equally with those who rend it, it is not unreasonable that they who receive the Body with unclean thoughts should suffer the same punishment as those who rent it with the nails. Observe at least how fearful a punishment Paul declares, when he says, “He that despised Moses' law dies without mercy under two or three witnesses; of how much sorer punishment, suppose ye, shall he be thought worthy, who has trodden under foot the Son of God, and has counted the blood of the covenant, wherewith he was sanctified, an unholy thing?” Take we then heed to ourselves, beloved, we who enjoy such blessings; and if we desire to utter any shameful word, or perceive ourselves hurried away by wrath or any like passion, let us consider of what things we have been deemed worthy, of how great a Spirit we have partaken, and this consideration shall be a sobering of our unreasonable passions. For how long shall we be nailed to present things? How long shall it be before we rouse ourselves? How long shall we neglect our own salvation? Let us bear in mind of what things Christ has deemed us worthy, let us give thanks, let us glorify Him, not by our faith alone, but also by our very works, that we may obtain the good things that are to come, through the grace and lovingkindness of our Lord Jesus Christ, by whom and with whom, to the Father and the Holy Ghost be glory, now and ever and world without end. Amen.
Source: Homilies on the Gospel of John (New Advent)