7. We may sometimes satisfy two obligations by one and the same action, as when a day of abstinence, on account of a vigil, falls on a Friday, or a day of obligation falls on a Sunday. Sometimes, however, the nature of the obligation or the presumed will of the legislator prohibits this being done. If a confessor imposed the hearing of Mass for sacramental penance, it would ordinarily be intended that a Mass not otherwise of precept should be heard. Nothing hinders the simultaneous fulfilment of two different obligations by actions which do not clash. A priest may well say his breviary while hearing a Mass of ob'igation.
8. If the whole of an obligation cannot be fulfilled, we are not thereby excused from fulfilling a part, if the matter is capable of being divided, and thus in some degree the end of the law is secured. If a priest, for example, cannot say the whole breviary, he must say what he can, if the portion which he can say be considerable and the form prescribed by the Church be observed. However, if a Bishop could not go the whole way to Rome to make his visit ad limina, there would be no obligation of going as far as he could.
9. When a fixed time is appointed for the fulfilment of an obligation, sometimes, according to the will of the legislator, after the term has passed, the law no longer binds; sometimes, on the other hand, the obligation must still be fulfilled. Thus, if a priest lawfully or unlawfully has omitted his breviary, he is not bound to make it up on the following day, or if one of the faithful miss Mass on a Sunday, he is not bound to supply the omission by hearing it on a week day. On the other hand, if a debt has not been paid on the date agreed on, it must be paid as soon as -possible afterward, and if the Easter Communion has not been made at the proper time there still remains the duty of making it.
