ITE, MISSA EST («Go, the dismissal is given»). — The dismissal in the Roman Mass, pronounced by the celebrant (in a Solemn Mass by the deacon), is first attested in the Ordo of John Archicantor, from the year 680 (ed. C. Silva-Tarouca, G. «Archicantor» of St. Peter’s in Rome and the Roman Ordo composed by him, in Atti della Pont. accad. romana di archeol., Memorie, I, 1 [1923], p. 201) and in the Ordo Romanus, I, 21 (PL 78, 948). But since the word missa, rather than the classical missio, is still used in the original sense of a dismissal, precisely the congedo of a solemn assembly or audience, the I. m. e. is already found in the 4th century, that is, in the early days of the use of Latin in the Roman liturgy, while later Missa took on another meaning (= the end of the assembly).
The dismissal was given following the ancient custom of dismissing public assemblies, solemn audiences—e.g., imperial and Byzantine ones—judicial sessions, religious ceremonies (or at least not allowing anyone to leave before being dismissed), as noted by Avitus of Vienne in 500: «In ecclesiastical palaces, where the missa is pronounced to be given, when the people are dismissed from the observance» (Ep. I: PL 59, 199). Already Tertullian seems to allude to it when he writes (De anima, 9): «post transacta sollemnia dimissa plebe». St. Augustine also speaks of the missa, i.e., the dismissal of the catechumens: «Post sermonem fiat missa catechumenorum, manebunt fideles» (Serm. 49, 8). And in the Peregrinatio Aetheriae (25, 1 and 29, 3, 5) missa is also found in the sense of dismissal. Florus explains the same sense when he writes (De exposit. missae, 92: PL 119, 72): missa = dimissio.
The word Ite is common to all rites, while missa est exists only in the Latin rite; in the others (Greek, Byzantine, Ambrosian) it is followed by in pace, or a similar phrase.
Until the 11th century, the I., m. e. was said at every Mass, whether festive or ferial; from this century, according to the author of the Micrologus (PL 151, 1011), on days of penance or when other canonical hours follow, it is changed to Bene dicamus Domino (v.), and in Masses for the dead Requiesca(n) in pace is used (according to Beleth, 12th century: PL 202, 56: «ex sola consuetudine generali»). It was pronounced («the deacon... sings in a raised voice»: Smaragdis, In Regulam s. Benedicti, 17: PL 102, 837) always in a more solemn tone already in the 9th century; today it is normally sung in the tone of the Kyrie. Tropes began to be used for the I., m. e. from the 10th century. As an announcement to the people, it is said facing the people, while Benedictus Dominus and Requiesca(n) in pace, being prayers, are said facing the altar, and the celebrant recites them together with the deacon.
Before the I., m. e., the celebrant greets the people with Dominus vobiscum, and they respond with the religious thanksgiving Deo gratias, just as at the readings; in other rites, e.g., the Ambrosian, the people respond In nomine Domini.