The third commandment of the law of God requires that we “keep holy the Sabbath day” (Ex 20:8), and in the Old Testament God Himself had more exactly defined how to fulfill this obligation. In the New Law, the Church has determined that the divine precept is to be fulfilled by the attendance to Mass on Sundays and holy days. This is an obligation—under pain of mortal sin—for each and every Catholic aged seven and older, who has the habitual use of reason.
To fulfill the ecclesiastical precept of attending Mass the first condition is the physical presence there where the Mass is celebrated, in such a manner that the actions of the priest may be followed. It is not required, however, to be inside the church, not even to see or hear the priest. It is enough to be part of those who hear the Mass (e.g., from the sacristy, or a side chapel, or behind a column, or in just outside if the church is crowded) and can follow it in some way, by the sound of the bell or the gestures of the other attendees. Thus, even outside the church building one can still assist at Mass for as long as one stays united with the group of faithful inside.
For lack of this physical presence, one who hears Mass on radio or television, or follows its online streaming, or who remains so far from the group of the attendees that he cannot be considered as being part of them does not fulfill the precept.
This presence must be continual during the whole Mass. The Mass must be whole and entire, that is, one must be physically present from beginning to end, from the first sign of the cross until the Last Gospel inclusively. If anyone voluntarily, on purpose or by culpable negligence, omits any notable part of it commits a sin.
In order to determine which part is considered notable, and therefore the gravity of the sin, it is necessary to take into account the dignity of the parts missed and the duration of the absence.
The essence of the Sacrifice consists in the double consecration, completed by the priest’s Communion, whereby the victim is consumed. Therefore, whoever arrives after the twofold Consecration or departs before the celebrant’s Communion has definitively missed the Mass and must attend another Mass to fulfill the precept. If he fails to do so, he commits a grave sin.
On the other hand, it is a venial sin to culpably miss out on a non-essential part of the Mass (for example, from the beginning until the beginning of the Offertory, or all that follows after Communion, or from the preface until the consecration or from the consecration to the Pater Noster). He who arrives late at Mass is obliged to supply the part that he omitted, unless it is materially or morally impossible (for example, because it is the last Mass or he must be absent by force).
The fulfillment of the precept also requires the religious, devout attention of the mind. Attention is the application of the mind to what is being done. It may be internal or external, depending on whether the mind is fixed or applied to the action being performed or avoids any external action that may hinder internal attention.
To validly hear the Mass at least real external attention is required. Thus, for lack of it, he does not hear Mass who during it reads a book entirely profane, or talks at length with the neighbor, or looks carefully at the images or architecture of the temple, or is fast asleep.
A certain interior attention, or presence of mind, is required so that this is truly a human act, and not just a simple physical presence. The interior attention can be: a) material, that is, to the words and actions of the priest; b) literal, that is, to the meaning of those same words and actions, and c) spiritual or mystical, doing acts of love of God or reciting pious prayers (v.gr., the rosary). Any of them is enough to fulfill the precept piously.
Moral theologians have discussed the question of whether the one who is confessing fulfills the precept. Some have said no, because confession requires all the attention of the penitent, even the external attention. Others have said yes, as long as one intends to hear Mass and attend to it as much as possible. In practice this second opinion can be followed, especially if it would be burdensome for the penitent to wait for the end of the Mass or there would be a danger of not being able to receive Communion, etc., since, undoubtedly, the mind of the Church is to facilitate the frequency of sacraments for the faithful, and it is not entirely impossible to pay some confused attention to the Holy Mass even during confession. It would be appropriate, however, to interrupt the confession during the consecration of the two species, remaining at that time collected and attentive.
Affability is friendliness, the virtue that impels us to put in our words and external actions what can contribute to make friendly and pleasant the relations with our neighbors It is an eminently social virtue, morally necessary for human coexistence, and one of the most delicate and unmistakable signs of an authentic Christian spirit.
Its manifestations are multiple, all exciting the sympathy and affection of those around us – kindness, simple and natural praise, indulgence, gratitude manifested with enthusiasm, politeness in words and manners, etc.
Nonetheless, as it is a moral virtue, affability must always be maintained in a just mean, since it can be sinned against by excess (flattery) and by defect (quarreling, spirit of contradiction).
Flattery is the sin of the one who tries to please someone in a disorderly or excessive way to obtain from him some advantage of his own. Deep down, it always implies hypocrisy and selfishness. As Saint Thomas says: “Friendship before said, or affability, even if it has as its own purpose to please those around it, however it should not fear, if necessary, displeasing to get a good or to avoid an evil. Indeed, if one wants to converse with another with the intention of pleasing him always and never contradicting him, he excels in his affability and therefore sins excessively. If he does this out of sheer joviality, he may be called kind according to Aristotle; but, if he does so seeking his own benefit or interest, he incurs the sin of flattery. However, the name of flattery is commonly extended to all those who inordinately seek to please others with words or deeds in the ordinary dealings” (II-II,115,1).
Answering the objection that praising or wanting to please everyone is not a sin, since Saint Paul says of himself that “I try to please everyone in everything” (I Cor. 10,33), the Angelic Doctor writes that to praise another can be good or bad action, as certain requirements are observed or neglected. In fact, if praise is intended, observing the right circumstances, to satisfy one and to encourage him in his work or to encourage him in the pursuit of his good works, it is the fruit of the above virtue of affability. Instead, it is flattery when praise falls on something that should not be praised, either because it is a bad or sinful thing, or because the foundation for such praise is not clear, or when it is to be feared that praise is for the other motive of vainglory. It is also good to want to please men in order to encourage charity and encourage others to progress in virtue. On the contrary, it is a sin to want to please them for reasons of vainglory, or of personal interest, or in bad things.
Quarreling, or the spirit of contradiction, is a sin that is opposed by defect to affability, and consists in frequently and systematically opposing the opinion of others with the intention of contradicting them or, at least, of not pleasing them.
If the contradiction to the words of the neighbor proceeds from a lack of love for him, it directly opposes charity; if it is done with anger, it is contrary to meekness, and if it is intended to grieve the neighbor or not to please him, constitutes properly the sin of litigation (or spirit of contradiction), which is directly opposed to affability.
In itself, quarreling is a more serious sin than flattery, because it is more radically opposed to affability, which in itself tends to please rather than to grieve. However, we must take into account the external motives that impel us to commit these sins. And, according to them, sometimes flattery is more serious, when it tries, for example, to obtain by deception an honor or an unjust profit. Others, on the other hand, are more serious litigation; for example, when the truth is challenged or the contrary is despised or ridiculed (II-II,116,2).