(Taken from Notes Made at the Conferences of Dom Prosper Guéranger)
Whilst the Choir is singing these several pieces [Gradual and Alleluia or Tract], the Deacon takes the Book of the Gospels, and puts it upon the Altar, because the Altar represents our Lord; and he thus signifies the identity existing between the Word of God, which is heard in the Gospel, and Christ Jesus. The Priest does not incense the Book, but he blesses the incense, an act which is not permitted to the Deacon. The incense having been blessed, the Deacon kneels upon the top step of the Altar, and says the prayer Munda cor meum. In that prayer, he asks of God, that his heart and his lips may be purified, to the end that he may worthily proclaim the holy Gospel. He there alludes to the coal of fire, with which a Seraph touched the lips of the Prophet Isaias, in order to purify him, and fit him to make known the inspirations received from the Holy Ghost. (Is. vi. 5-7.) This same Prayer is also said at private Masses, by the Priest. After the prayer, the Deacon takes the Book from the Altar; and, kneeling before the Priest, asks for a blessing, because he is going to read:
Jube, Domne, benedicere; Please, Father [sir], give me a blessing. In a private Mass, the Priest asks the blessing of God, saying: Jube, Domine, benedicere! [Please, Lord, give me a blessing] and then he answers in the words of the blessing, making such changes as are necessary for applying them to himself. Having received the blessing, the Deacon kisses the hand of the Priest, who, for this purpose, should place his hand on the Book of the Gospels, which he thus virtually gives to the Deacon, commissioning him to read it in his name.
A procession is then formed towards the Gospel-Ambo; and there the Deacon begins with this solemn expression: Dominus vobiscum. It is the only occasion on which the Deacon is allowed to use these words [outside of the Exsultet at the Easter Vigil]: and his present use of them is equivalent to his preparing the Faithful; as though he said to them: You are about to hear the Word of God, the eternal Word: it is a great grace for you all: may, then, the Lord be with you! May he enlighten you, and nourish you with His Word!
The people answer him, saying: Et cum spiritu tuo. Then, the Deacon announces the title of the passage he is going to give them: he tells it them in these words: Initium, or Sequentia sancti Evangelii [Beginning or Continuation of the Holy Gospel]; and whilst saying this, he makes the sign of the Cross upon the Book, at the place where begins the text of the Gospel. He, at the same time, signs himself on the forehead, the lips, and the breast, asking, in virtue of the Cross, which is the source of all grace, that he may always have the Gospel in his heart, and on his lips, and that he may never be ashamed of it. He then takes the thurible, and incenses the Book three times; whilst the Faithful, in answer to the announcement of the Good Tidings, give
thanks and glory to our Lord Jesus Christ, whose Word is now going to be heard: Gloria tibi, Domine. [Glory to you, Lord] It is now time to sing the holy Gospel. The Deacon joins his hands; but does not lean them on the Book, as that would be too great a familiarity with an object so sacred as is the Book, which contains the expression of the Eternal Word. The Deacon having completed what he had to sing, the Subdeacon takes the open Book to the Celebrant, who kisses the first words of the sacred text, saying: Per evangelica dicta deleantur nostra delicta; May our sins be wiped away by these words of the Gospel. In this formula, (which is sometimes used as one of the Blessings at Matins,) we find a species of rhyme, which denotes a medieval origin. Meanwhile, the Deacon turns towards the Priest, in whose name he has been singing the Gospel; and, taking the thurible, thrice honours him with incense. The Priest is the only one to receive this honour at this portion of the Liturgy.
The Priest, who says Mass without Deacon and Subdeacon, should, when he reads the Gospel, so place the Missal, that he himself shall be somewhat turned towards the North. It is the same with the Deacon; he stands facing the North when he sings the Gospel because, according to the word of the Prophet Jeremias (i. 14.) From the North, shall all evil break forth upon all the inhabitants of the Land. It is for the same mysterious reason, that in the Baptism of adults, the Catechumen is put, so as to face the North, when uttering his renunciation of Satan. Formerly, in the larger churches, there were erected two Ambos, or pulpits: one for the Epistle, and the other for the Gospel. At present, we do not find these two Ambos, except in the two churches at Rome, St. Clement, and St. Laurence-outside-the-walls. They were used, also, in St. Paul’s, before its restoration. It was at the Ambo, that was placed the Paschal Candle, during the forty days preceding the Feast of the Ascension.
We should notice the difference, wherewith the Church would have the Epistle and the Gospel announced in the Mass. As to the Epistle, it is merely preceded by the Subdeacon’s saying whence is taken the Passage which he is going to sing; whereas, the Gospel is always preceded by the words: Dominus vobiscum. The reason is, that in the Epistle, it is but the servant that speaks to us; but, in the Gospel, it is the word of the Master himself, which we are about to hear; and, therefore, a means is taken for exciting the attention of the Faithful... In Masses for the Dead, the Deacon does not ask the Priest’s blessing, when about to sing the Gospel. As the asking such a blessing is, more or less, a ceremony expressive of Joy, it is omitted, because of the sadness and mourning which accompany a Requiem Mass. Neither are torches borne at the Ambo; nor does the Priest kiss the Book at the end of the Gospel. For the same reason, the Deacon does not kiss the Priest’s hand, after having taken the book from off the Altar.