The omission of the entire office of a day, the seven canonical hours, is held by some theologians to carry the guilt of seven mortal sins. Because, there is a different precept for each hour and the omission of each hour violates a precept. The Salamenticenses think this opinion probable. The more common and the more correct opinion is that by such omission only one sin is committed. And the theologians who hold this opinion say that the recitation of the canonical hours is imposed under one precept only, and hence there is only one obligation embracing the seven hours. This is the opinion of St. Alphonsus (n. 148) who quotes several authors (including Lessius, Sanchez and St. Antoninus) in support. If a person in Holy Orders omit several hours with a retractation, or a moral interruption in his sinful intentions, he may commit several mortal sins, because all the omissions, which in themselves are grave matter, may become independent of each other by the interruption and renewal of the intention (St. Alphonsus, n. 148).
What must a person do who has a doubt that he has omitted something in his recitation of the office? Is he bound to make assurance doubly sure by reciting the part of which he doubts?
If the doubt be a positive doubt, that is, if he have good reason to believe that he has recited it, he is not bound to anything further regarding the part in question. For instance, if a priest remembers having started the recitation of a lesson, and in a short time finds himself at the end of it, and cannot be sure if he have recited it, the presumption is in favour of the priest and of the recitation, because it is his custom to recite completely whatever part he commences. He has, thus, moral certainty that he has satisfied the precept, and it is not necessary to repeat it; if the necessity for repetition be admitted in such a case, a fruitful source of scruples is opened up.
On the other hand, if the doubt be negative—that is to say, if a person has no reasonable motive for believing that he has recited the full office or the full hour, he is bound to recite the part omitted, because in such a doubt, the precept of recitation is, as the theologians say, "in possession." (St. Alphonsus, n. 150).
It is not allowed to change anything nor to add anything to the daily office without permission. The Sacred Congregation of Rites (10 June, 1690, n. 3222) replied to a query, that in saints' offices nothing is to be added and nothing is to be changed, and this reply applies to all sorts of offices, old and new.
THE ORDER TO BE OBSERVED IN RECITING THE DIVINE OFFICE.
In reciting the Divine Office two points of order are to be noted: (1) the order or arrangement of offices, (2) the order or arrangement of Hours. The order of offices indicates which office is to be said on each day as laid down in the calendar. The order of the Hours points out which of the seven hours should be recited, firstly, secondly, etc., Matins, Lauds, Prime, Terce, etc. It is of obligation to observe both orders. But is it a sin to change wilfully the order of the office? It is not, if there be a reasonable cause for the change. For instance, if a priest cannot say the office proper to his diocese on a certain day, but says some other approved office, the change is not a sin. But if a priest, ex industria, substitute one office for another, it is per se a venial sin; but if an office be said which is very much shorter than the calendar office, or if this changing or substituting be so frequent as to disturb gravely the good order of the year's offices, the sin may be (and, according to some authors, is) a mortal sin.
It is asked whether a person fulfils his debt to the Church if he has recited by mistake an office other than the one assigned in the calendar of the day. Theologians teach that such a recitation fulfils the debt. The Church does not wish to impose a second recitation, and her axiom "officium pro officio valet" holds, provided always that the order of the psalms as laid down in the new psaltery is followed. This order is necessary always for validity. However, if the substituted office be very much shorter than the omitted office, it is advised to equalise them by reciting the psalms of Matins, This is a counsel and was not laid down by theologians as an obligation.
An office thus omitted is not to be transferred to another day (S.C.R., June 17th, 1673). The office may be omitted altogether for that year. If there be leisure the omitted office should be recited. This practice is in conformity with the spirit of the liturgy and with the right order of the calendar. The Sacred Congregation of Rites, questioned on this matter, replied sic debere fieri, such should be done. If a priest recites by mistake one day's office for another (e.g., the Tuesday office on a Monday) he is bound to recite Tuesday's office on Tuesday (St. Alphonsus). If, however, after a portion of the office has been read, it is noticed that a mistake has been made in reading the calendar or the Ordo, and that the office partly recited is not the office of the current day, what is to be done? If the priest has without fault made the mistake of reciting some office not ascribed to the current day, he is not bound to repeat the part already recited (e.g., Matins); it is sufficient, valid and lawful to follow the correct office in the following Hours. The priest reciting is not bound to repeat even part of an hour, if he finds out his mistake during the recitation of even a small hour. And he may finish the psalm or hymn or prayer which he was reciting when he discovered his mistake, and he may then take up the correct office at the part or hour at which he leaves off, or he may finish the Hour at which he was engaged. The former solution of the difficulty seems the better, as it more accurately agrees with the maxim, error corrigatur ubi apprehenditur. If the error in the selecting of the office has been wilful, say, through gross carelessness, and is the fault of the priest who changes a notable part of a canonical Hour, he is obliged—the more probable opinion teaches—to repeat the full Hour, and this obligation binds under pain of venial sin—i.e., the obligation to recite the office in the prescribed manner.
What is a person bound to do who forgets part of an Hour—is he obliged to repeat the full Hour?