Visiting priests should be gladly welcomed to Eucharistic concelebration, as long as their priestly standing is ascertained.
Where there is a large number of priests, concelebration may take place even several times on the same day, wherever necessity or pastoral benefit suggest it. Nevertheless, it must be held at different times or in distinct sacred places.102Cf. Sacred Congregation of Rites, Instruction Eucharisticum mysterium, On the worship of the Eucharist, 25 May 1967, no. 47: AAS 59 (1967), p. 566.
It is for the Bishop, in accordance with the norm of law, to regulate the discipline for concelebration in all churches and oratories of his diocese.
To be held in high regard is that concelebration in which the priests of each diocese concelebrate with their own Bishop at a stational Mass, especially on the more solemn days of the liturgical year, at the Ordination Mass of a new Bishop of the diocese or of his Coadjutor or Auxiliary, at the Chrism Mass, at the Evening Mass of the Lord’s Supper, at celebrations of the Founder Saint of a local Church or the Patron of the diocese, on anniversaries of the Bishop, and, lastly, on the occasion of a Synod or a pastoral visitation. For this same reason, concelebration is recommended whenever priests gather together with their own Bishop either on the occasion of a retreat or at any other meeting. In these instances the sign of the unity of the priesthood and also of the Church inherent in every concelebration is made more clearly manifest.103Cf. Sacred Congregation of Rites, Instruction Eucharisticum mysterium, On the worship of the Eucharist, 25 May 1967, no. 47: AAS 59 (1967), p. 565.
For a particular reason, having to do either with the significance of the rite or of the festivity, the faculty is given to celebrate or concelebrate more than once on the same day in the following cases: A priest who has celebrated or concelebrated the Chrism Mass on Holy Thursday may also celebrate or concelebrate the Evening Mass of the Lord’s Supper; A priest who has celebrated or concelebrated the Mass of the Easter Vigil may celebrate or concelebrate Mass during the day on Easter Sunday; On the Nativity of the Lord (Christmas Day), all priests may celebrate or concelebrate three Masses, provided the Masses are celebrated at their proper times of day; On the Commemoration of All the Faithful Departed (All Souls’ Day), all priests may celebrate or concelebrate three Masses, provided that the celebrations take place at different times, and that the norms established regarding the application of second and third Masses are observed;104Cf. Benedict XV, Apostolic Constitution Incruentum altaris sacrificium, 10 August 1915: AAS 7 (1915), pp. 401-404. A priest who concelebrates with the Bishop or his delegate at a Synod or pastoral visitation, or concelebrates on the occasion of a meeting of priests, may celebrate Mass again for the benefit of the faithful. This holds also, with due regard for the prescriptions of law, for groups of religious.
A concelebrated Mass, whatever its form, is arranged in accordance with the norms commonly in force (cf. nos. 112-198), except for those matters that are to be observed, even with appropriate adaptation to circumstances, as set forth below.
No one is ever to enter into a concelebration or to be admitted as a concelebrant once the Mass has already begun.
In the sanctuary there should be prepared Seats and texts for the concelebrating priests; On the credence table: a chalice of sufficient size or else several chalices.
If a deacon is not present, his proper duties are to be carried out by some of the concelebrants. In the absence also of other ministers, their proper parts may be entrusted to other suitable members of the faithful; otherwise, they are carried out by some of the concelebrants.
In the vesting room or other suitable place, the concelebrants put on the sacred vestments they customarily wear when celebrating Mass individually. Should, however, a good reason arise, (e.g., a large number of concelebrants or a lack of vestments), concelebrants other than the principal celebrant may omit the chasuble and simply wear the stole over the alb.