A: The “Sunday obligation” is found in the Code of Canon Law, where it states, “On Sundays and other holy days of obligation, the faithful are obliged to participate in the Mass. Moreover, they are to abstain from those works and affairs which hinder the worship of God, the joy proper to the Lord’s day, or the suitable relaxation of mind and body” (canon 1247). This obligation is part of the responsibility of every Christian “to lead a holy life and to promote the growth of the Church and its continual sanctification, according to their own station” (canon 210).
The Catechism of the Catholic Church explains that “the Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation, unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor. Those who deliberately fail in this obligation commit a grave sin” (2181).
Two things should be noted as regards the Sunday obligation. First, Catholics are required to attend Mass on Sundays and holy days, but are not required to receive Holy Communion each time they attend Mass. Second, the law makes no distinction about “how much” of the Mass we must attend. Because it makes no distinction, in my opinion, we must – unless excused – participate in the entirety of the Mass, from beginning to end, in order to fulfill the Sunday obligation, in addition to abstaining from those things which hinder the worship of God and suitable relaxation. Of course, there are times when circumstances beyond our control may make us arrive late to the Holy Mass, but these situations should not be common occurrences. It is difficult to imagine too many situations (excepting sudden emergencies) in which departing from the Holy Mass only a minute or two before the conclusion would be necessary.
The Mass begins with the Introductory Rites, which “precede the Liturgy of the Word, namely, the Entrance, the Greeting, the Penitential Act, the Kyrie, the Gloria in excelsis (Glory to God in the highest), and Collect, [and] have the character of a beginning, an introduction, and a preparation” (GIRM, 46). The Holy Mass begins, then, with the entrance of the priest (and the ministers), accompanied, if there is one, by a chant or hymn.
The Mass finishes with the Concluding Rites, which may include announcements and always includes the Priest’s Greeting and Blessing, the Dismissal, and, finally, “the kissing of the altar by the Priest and the Deacon, followed by a profound bow to the altar by the Priest, the Deacon, and the other ministers,” unless the tabernacle is located in the sanctuary, toward which all genuflect instead (GIRM, 90d).
Given what the Lord Jesus has done for us, the fulfillment of the Sunday obligation ought to be done out of a sense of devotion and love. Indeed, because “the Christian faithful are to hold the Most Holy Eucharist in highest honor, taking an active part in the celebration of the most august sacrifice, receiving this sacrament most devoutly and frequently, and worshipping it with highest adoration,” the question of “how much” of the Mass one must attend ought not enter into the thoughts of a Catholic. Our love of the Lord Jesus and for the community of the faithful should be such that we have a longing to worship together at the altar of the Lord.
—Answered by Father Daren Zehnle, Diocese of Springfield (IL)