Sections 
THE SANCTUS
The Sanctus (Holy, Holy, Holy) became an integral part of the Eucharistic Prayer (The Prayer of Thanksgiving) in both the Eastern and Western churches from before the year 400 A.D. The Sanctus forms the conclusion of the variable part of the prayer called the Preface.
Its text is composed of two parts, both inspired in Scripture. The two conclude with the phrase: “Hosanna in the highest.”
The justaposition of both parts highlight two very different aspects of God. The first part focuses on the awe and surpassing wonder before the divine majesty, and in the second, the humility of Jesus, God made man.
“Holy, Holy, Holy Lord, God of power and might,heaven and earth are full of your glory.
Hosanna in the highest.
Blessed is he who comes in the name
of the Lord.
Hosanna in the highest.”
Holy is God’s own name. More than simply a moral quality of God, it indicates the infinite quality itself of the divine being: He alone is Holy (Lev. 11:44), and at the same time He is the only “fountain of all holiness” (EP II).
The first section of this prayer evokes the image of God as a transcendent Being seated in His throne with the unceasing liturgy gathered around Him, just as we find described in the book of the prophet Isaiah and in Revelation. In Isaiah’s description, he himself is initiated into the charism of his vocation through an impressive heavenly vision: “In the year King Uzziah died, I saw the Lord seated on a high and lofty throne, with the train of his garment filling the temple. Seraphim were stationed above; each of them had six wings: with two they veiled their faces, with two they veiled their feet, and with two they hovered aloft. "Holy, holy, holy is the LORD of hosts!" they cried one to the other. "All the earth is filled with his glory!" At the sound of that cry, the frame of the door shook and the house was filled with smoke. Then I said, "Woe to me, I am doomed! For I am a man of unclean lips, living among a people of unclean lips; yet my eyes have seen the King, the LORD of hosts!” (Isaiah 6:1-5)
At the end of this scene, one of the seraphim takes a flaming rod that had been taken from the altar and consumes Isaiah’s sin, purifying his lips.
The visionary of the book of Revelation suffers a similar experience, making deliberate allusion to the passage from Isaiah:
“At once I was caught up in spirit. A throne was there in heaven, and on the throne sat one whose appearance sparkling like jasper and carnelian. Around the throne was a halo as brilliant as an emerald. Surrounding the throne I saw twenty-four other thrones on which twenty-four elders sat, dressed in white garments and with gold crowns on their heads.
From the throne came flashes of lightning, rumblings, and peals of thunder. Seven flaming torches burned in front of the throne, which are the seven spirits of God. In front of the throne was something that resembled a sea of glass like crystal. In the center and around the throne, there were four living creatures covered with eyes in front and in back. The first creature resembled a lion, the second was like a calf, the third had a face like that of a human being, and the fourth looked like an eagle in flight. The four living creatures, each of them with six wings, were covered with eyes inside and out. Day and night they do not stop exclaiming: "Holy, holy, holy is the Lord God almighty, who was, and who is, and who is to come." (Rev. 4:2-8)
The second part of the Sanctus has its origin in the triunphant entry of Jesus into Jerusalem. The passage contains a description of the suprising image of a humble God arriving into the Holy City mounted on a donkey amidst shouts of praise from the people who rejoice at the arrival of their salvation:
“When they drew near Jerusalem and came to Bethphage on the Mount of Olives, Jesus sent two disciples, saying to them, "Go into the village opposite you, and immediately you will find an ass tethered, and a colt with her. Untie them and bring them here to me. And if anyone should say anything to you, reply, 'The master has need of them.' Then he will send them at once." This happened so that what had been spoken through the prophet might be fulfilled: "Say to daughter Zion, 'Behold, your king comes to you, meek and riding on an ass, and on a colt, the foal of a beast of burden.'” The disciples went and did as Jesus had ordered them. They brought the ass and the colt and laid their cloaks over them, and he sat upon them. The very large crowd spread their cloaks on the road, while others cut branches from the trees and strewed them on the road. The crowds preceding him and those following kept crying out and saying: "Hosanna to the Son of David; blessed is he who comes in the name of the Lord; hosanna in the highest."(Mt. 21:1-9)
The apparent contradiction in the descriptions of God in the two parts of the Sanctus is a result of the prophetic nature of the former and the escatological nature of the latter. Jesus appears as the humble prophet who comes to a city where He will be rejected and executed. But He is also the herald of God who proclaims a new era, and who changes the entire cosmos as He destroys the false distinction that man had made between the pure and the impure. He enters into the Temple and expells the money-changers who had converted the house of God into a den of thieves. If the people had not sang His praises, surely the very stones would have done so (Lk. 19:40).
In the celebration of the Eucharist, sacramental memorial of the Death of the Lord, the Christian people offer Jesus the same praises that the people offered Him in His entrance into Jerusalem, when He went to live the Passion.
The Sanctus was sung frequently by the entire liturgical assembly in the first centuries as well as in the Middle Ages. Charlemagne gave order that the Sanctus be sung by both clerics and faithful in his Admonitio generalis, written for his kingdom in the year 789.
The Preface, and the Sanctus in particular, are a part of the mass that should most be sung. In light of this fact, we should remind ourselves of the liturgical norm, not always observed: “In selecting the parts which are to be sung, one should start with those that are by their nature of greater importance, and especially those which are to be sung by the priest or by the ministers, with the people replying, or those which are to be sung by the priest and people together. The other parts may be gradually added according as they are proper to the people alone or to the choir alone.” (Musicam Sacram, 7)
