OREMUS (LET US PRAY). - A generic invitation in the Roman rite from the celebrant to the faithful before the prayers at Mass (Collects, Secreta, Postcommunion, Pater noster), in the Office and on other occasions.
On Good Friday a brief allocution is added to the O., specifying the intention of the prayer: «Oremus, dilectissimi nobis, pro Ecclesia... pro Papa... ut Deus purget... auferat... indulgeat». To this invitation, more or less specified, there corresponded a prayer of the people, and in fact until the 9th century (cod. Vat. Ottobon. 313, in H. Lietzmann, Das Sacramentarium Gregorianum, Münster in W., 79, 2, n. 9) a few moments of silent prayer followed. Outside of Easter, on weekdays or on penitential days, the people knelt at the deacon's announcement Flectamus genua: then at a second announcement: Levate they rose again. The priest, as on feast days, after a few moments of prayer, gathered aloud the common sentiments of the faithful in a brief oration, later called the «Collect», to which the people acclaimed Amen. As this invitation was gradually shortened and the subsequent interval of silent prayer omitted, the O. became a simple introductory formula, joined to and immediately followed by the priest's prayer formula; the ancient formula remains on the weekdays of the Ember Days, of Good Friday and of the Easter night. In the Collect of the Ambrosian rite the invitation of the O. is never used. In the Gallican liturgy the first Collect of the day is preceded by a more or less lengthy Preface, sometimes also in the form of a small homily, spoken by the bishop to invite prayer and to explain the festivity of the day; for the other orations the invitation is not known, perhaps the O. was used, as in the Roman rite (L. Duchesne, Origines du culte chrétien, Paris 1925, p. 113). The Mozarabic liturgy, on the other hand, uses the O. twice, before the Agios and the Pater noster. In the Eastern rites the invitation, spoken by the deacon, is always followed by a response of the people Kyrie eleison or similar. The invitation, sometimes simple as in the Roman rite, is more specified and detailed, especially in the so-called oration of the faithful. During the prayer of the deacon with the people, the oration is recited by the priest (Byzantine rite). In practical use, the word O. is also employed to mean the whole following oration to be said according to the circumstance.