Catholic Encyclopedia (1913)/Ite Missa Est
This is the versicle chanted in the Roman Rite by the deacon at the end of Mass, after the Post-Communions. It is our formula of the old dismissal (apolysis) still contained in all liturgies. It is undoubtedly one of the most ancient Roman formulæ, as may be seen from its archaic and difficult form. All the three oldest Roman Ordines contain it. "Ordo Rom. I" says: "When the prayer [Post-Communion] is over, that one of the deacons appointed by the archdeacon looks towards the pontiff to receive a sign from him and then says to the people: Ite missa est. They answer: Deo gratias (ed. Atchley, London, 1905, p. 144. See also "Ordo Rom. II", 15; "Ordo Rom. III", 18). The medieval commentators were much exercised to explain the meaning of the strange expression. Durandus (Rationale, IV, 57) suggests several interpretations. It has been thought that a word is omitted: Ite, missa est finita; or est is taken absolutely, as meaning "exists", is now an accomplished fact". The real explanation seems to lie rather in interpreting correctly the word missa. Before it became the technical name of the holy Liturgy in the Roman Rite, it meant simply "dismissal". The form missa for missio is like that of collecta (for collectio), ascensa (ascensio), etc. So Ite missa est should be translated "Go it is the dismissal." (See Florus the Deacon, "De expositione Missæ", P.L., CIX, 72.) On certain days which have the character of fasting or penance, this versicle is replaced by the words Benedicamus Domino. The fact is noticed by medieval liturgists (e.g., Durandus, IV, 57 — cf. "Micrologus", xxxiv; etc.) since about the eleventh century. The three Roman Ordines before the tenth century know only the form Ite missa est. The explanation is that originally the people were not dismissed on such days, but stayed in church for further prayers after Mass, suitable to fasting days (so Bona, "Rerum liturg. libri duo", II, xx, n.3). This is confirmed by a now extinct medieval custom of singing Benedicamus Domino at the end of midnight Mass at Christmas, because Lauds follow at once (Durandus, op. cit., IV, 57, §7). So the idea obtained that Ite missa est implies a festal Mass. Our present rule that it follows the Gloria in Excelsis (and therefore the Te Deum in the Office) is noted in "Micrologus" (xlvi). Either versicle was always answered by the obvious response Deo gratias, implying thanks that the Sacrifice has been offered — is now complete. At Requiems (since they have no Gloria) Ite missa est is not said. In this case the versicle is Requiescant in pace. The response is Amen. John Beleth (twelfth century) says that this arose "only from a general custom" ("Rat. div. offic." in P.L., CCII, 49). Till about the twelfth century the Ite missa est really ended the liturgy, as its form implies. In the First Roman Ordo, immediately after it the text continues: "Then the seven candlesticks are carried before the pontiff . . . to the sacristy" (ed. Atchley, p. 146). It was not till the sixteenth century (Missal of Pius V) that the accretions to the Mass that had gradually been introduced (Placeat, blessing, last Gospel — all originally private prayers) were definitely recognised as part of the liturgy to be said at the altar.
The corresponding dismissals in the other Western rites are: at Milan, V. "Procedamus in pace." R. "In nomine Christi"; Mozarabic, "Solemnia completa sunt in nomine D. N. I. C: votum nostrum sit acceptum cum pace." R. "Deo gratias" ("Missale Mixtum", P. L., LXXXV, 120). Of the Eastern rites that of the "Apostolic Constitutions" dismisses the people with the form: "Go in peace" (Brightman, "Eastern Liturgies", p. 27). The Antiochene and Byzantine Liturgies end with the deacon's announcement: "Let us go forth in peace." R. "In the name of the Lord"; and then a short "prayer of dismissal" said by the celebrant (op. cit., 67, 397); so also the Alexandrine Rite (ibid., 142): while the Nestorians have only a prayer and blessing by the celebrant (ibid., 303).
At high Mass, as soon as the last Post-Communion is ended, the celebrant and ministers go to the middle of the altar and stand in line. The celebrant turning to the people sings Dominus vobiscum (the usual introduction to any announcement), and remains facing them. When the choir has answered, the deacon turns round and, with hands joined, sings Ite missa est to its proper tone, the choir answering Deo gratias to the same notes. In the former Missal ten melodies were provided for various solemnities. The idea is to sing this last versicle to the tone of the first Kyrie eleison, so that Mass ends with the same chant as that with which it began. To carry this out more completely the new Vatican Missal provides nineteen tones, most of them very elaborate (for Ite missa est and Benedicamus Domino), corresponding to the various masses in the Kyriale". The tone of the first Kyrie should always be used. In figured masses the Ite missa est should be sung to the tone of the plain-song mass provided for the occasion. From Holy Saturday till White Saturday (Sabbatum in albis), inclusively, two Alleluias are added to both versicle and response; in this case they have a special melody (the first in the Missal), which does not correspond to the Kyrie. At Masses that have no Gloria in excelsis (therefore in the Office de tempore of Advent and Lent, vigils, and ember-days, except Maundy Thursday and Holy Saturday; at Votive Masses, except those of the B.V.M. when celebrated on Saturday, Votive Masses of Angels, and, for a grave cause, when violet vestments are not used in the Mass — "Rubr. Gen." of the Missal, viii, 4) the celebrant turns back to the altar after the Dominus vobiscum, and the deacon, facing the altar, sings, Benedicamus Domino, to the same tone (of the Kyrie); the answer is the same, Deo gratias. At all Requiems in the same manner he sings, to the tone provided in the Missal. Requiescant in pace (in the plural, even when Mass is said for one person — S. R. C., 22 Jan., 1678). R. Amen. As soon as the deacon has finished his versicle the celebrant turns back to the altar and waits; the deacon and subdeacon kneel on the suppedaneum. When the answer of the choir is finished the celebrant says the prayer Placeat and then gives the blessing. The celebrant himself says Benedicamus Domino or Requiescant in pace in a low voice while the deacon sings, because these are prayers. He does not say Ite missa est, because this is an announcement to the people. At a sung Mass the celebrant sings the deacon's part, at a low Mass he says it. Otherwise there is no change.
BERNOLD OF CONSTANCE in the "Micrologus" in "P.L"., CLI, 973-1022, xlvi; JOHN BELETH, "Rationale divinorum officiorum" in "P.L"., CII, 14-166, xlix; DURANDUS, "Rationale", IV, 57, and all the medieval commentators: BONA, "Rerum liturgicarum libri duo," xx; BENEDICT XIV, "De S. Missæ Sacrificio", II, xxiv; GIHR, "Das heilige Messopfer" (Freiburg im Br., 1897), 714-17; DE HERDT, "Sacræ Liturgiæ praxis "(Louvain, 1894), I, 481-83.