(a) The Time of Mass.—Mass may not be said on Good Friday, nor private Masses on Holy Thursday and Holy Saturday. Only one Mass may be said a day, except on Christmas Day and All Souls’ Day, and on other days when there is reason for bination or trination allowed by the Church. Ordinarily the hour for beginning Mass should not be earlier than one hour before dawn (i.e., in the latitude of New York from about 1:27 a.m. to 5:00 a.m., according to the season), nor later than one hour after noon. But the time is to be understood morally, and it is not a grave sin in being earlier or later than the times fixed, unless there is a difference of an entire hour (e.g., if one began Mass at 2:00 p.m.) and not just excuse or dispensation. The Holy See has extended to local Ordinaries the power to permit the daily celebration of Mass after noon, if the spiritual good of a considerable number of the faithful demands it (_Sacram Communionem_). The Holy See has also granted permission to Ordinaries to allow the celebration of an evening Mass on Palm Sunday accompanied by the blessing of palms and procession. On Holy Thursday the Mass of the Lord’s Supper must be celebrated at the most convenient hour, but not before 4:00 p.m. and not after 9:00 p.m.; Ordinaries may grant permission for one or even two low Masses (besides the principal Mass) to be celebrated in churches and public oratories, and for one in semi-public oratories within the same hours, 4:00-9:00 p.m. The proper hour for the Easter Vigil is that which permits the Mass of the Easter Vigil to be started around midnight. Permission may be granted to conduct the vigil at a time not before sunset (Dispositions and Regulations concerning the Holy Week Liturgy, Feb. 1, 1957, Sacred Congregation of Rites). One Christmas may be said at midnight. It is a serious sin to say Mass in less than a quarter of an hour, and a private Mass should not be prolonged beyond a half-hour.
(b) Place.—Mass may not be celebrated regularly except in a church or oratory that is at least blessed and is not polluted, execrated or interdicted. It must be said on an altar, and it would be a serious sin, except in grave or very grave necessity, to celebrate without at least one altar cloth or one lighted wax candle, or without a rubrical chalice, paten, or corporal (Canons 822, 823).
(c) Rites.—The principal rubrics of the Mass are gravely obligatory, for example, to use an acolyte unless excused by dispensation or necessity, to say each prayer of the Canon, and each part outside the Canon that occurs in every Mass (e.g., the prayers at the foot of the altar, the Gospel), to perform the main liturgical actions (e.g., the Offertory, the breaking of the host, the purification of the chalice). The secondary rubrics oblige under venial sin (see Canons 803, 812-819).
2713. Is it Lawful to Discontinue a Mass?—(a) To terminate Mass before the end has been reached is unlawful unless there be a serious reason; otherwise, disrespect is shown the Holy Sacrifice. A grave reason (e.g., sudden sickness) suffices if Mass be discontinued before the Consecration; a most grave reason (i.e., danger of death or of profanation of the Sacrament) if Mass be discontinued between the Consecration and the Communion. But a Mass that is broken off after the Consecration and before the Communion must be completed by the celebrant or another, at least if this can be done within an hour from the time of cessation; else the sacrifice is mutilated.
(b) To interrupt Mass is also unlawful without serious cause. Thus, a grave reason excuses an interruption outside the Canon, for example, to preach a sermon after the Gospel or Communion; but only a very grave reason excuses an interruption during the Canon, for example, a sick call to give a necessary Sacrament (Baptism, Penance, Extreme Unction, or Viaticum) to a dying person.
2714. Application of the Mass.—All the faithful, especially those who are present and also the celebrant himself, benefit by the Mass, but there is a special fruit reserved to those for whose intention the Mass is offered by the priest; for the Mass is a sacrifice of intercession, propitiation, and satisfaction, and since the priest acts in the person of Christ he may apply its benefits specially to some particular person or persons. In the following cases the celebrant is bound to make this application of the ministerial fruit of the Mass.
(a) In virtue of their office, pastors are seriously obliged to say Mass for their flocks. There is a natural obligation on account of the relationship between the pastor and the people, and there is also a divine obligation, inasmuch as the priest is appointed to offer gifts and sacrifices for sin (Heb., v, 1). The details of this duty, as to the time, place and person, are prescribed in Canons 306, 339, 466. There is a grave duty of saying for the people the number of Masses which the Church orders; but the non-observance of the circumstances is not a mortal sin, unless it happens frequently and without reason.
(b) In virtue of justice, a priest who has received a stipend is bound to apply the Mass for the intention of the donor, and to observe the conditions of the agreement (i.e., the time, place, and kind of Mass specified by the donor). The duty of application is a grave one, because the loss inflicted on the donor by non-application of the Mass to his intention is serious; the duty of observance of the accidental conditions, however, is not generally grave, but it becomes grave if its neglect inflicts serious harm (e.g., if the donor makes the date of the Mass a _conditio sine qua non_, or if the Mass must be said at once on account of an urgent and immediate necessity). Restitution is obligatory if the Mass is not applied, or if essential conditions are not complied with; it is obligatory _sub gravi_, if the stipend equals what is relatively grave matter in theft.
(c) In virtue of obedience, subjects are held to apply Masses for the intention of their prelates, secular or religious, though bishops are counselled to exact this most rarely. The obligation is grave or light according to the intention of the superior, but if the application is also due in justice to the giver of the stipend, there is a serious duty.
(d) In virtue of religion or fidelity, there is an obligation of application when a priest has vowed this to God, or freely promised it to man. The duty is grave or light according to the intention of the vower or promisor (see 2210, 2407). But if there is an onerous promise (e.g., in a society of priests whose members agree to say Mass for fellow-members who have died), the duty is one of justice. One Mass satisfies several free promises, if distinct Masses were not promised.