Regarding eating out on Sundays.
Only if one must do it would it be acceptable.
But without necessity, however, it is definitively a mortal sin. For you are doing something without necessity, and only for pleasure, convenience or sloth, and by it helping your fellow brother or sister into committing a possible mortal sin by working unnecessarily on a Sunday.
Now, since many people who are reading this have not been taught these concepts by modernist heretics, we must point out a few other things in this regard: servile works are forbidden on Sundays; people should not do laundry on Sundays; people should not do yard work (such as mowing the lawn, etc.) on Sundays; people should not shop food on Sundays unless they are starving etc... Exceptions to this would be work that absolutely must be done, such as helping others spiritually or bodily (as working in a hospital), or if you had to make a fire in your home so that you can be warm and survive is a work that are completely acceptable. If you are able to make your food for the whole family before the Sunday, you should do so. One should not spend the Sunday on making food for the family which may take several hours of the day. You may of course (if you don't have any prepared food) take time to make something small for you or the family which does not require much of your time or take some food that you already have and warm it up. You cannot cut wood on Sundays and you must restrict yourself to only do things that are absolutely necessary for survival. This, of course, implies some preplanning, but no one should refuse to obey the divine commandments since this action will undoubtedly lead to eternal damnation. An obedient person will see the beauty of God forcing man to rest from physical works.
To do other unnecessary works on Sundays is completely unacceptable unless you starve and don't have the means necessary to support your family. In the richer countries, even going so far as begging or receiving social welfare checks every month is far better than to do unnecessary work on Sundays, since this not only damns yourself, but also damns your employer. Your employer will in fact be punished for every single person he has allowed or forced (by threatening with layoffs) to work on Sundays. That can be thousands and thousands of people attacking one man for all eternity! What a horror!
If you have exhausted all the options for receiving an income, for ex: looking for another job or moving to another place, or any other lawful means of receiving an income, (like receiving social welfare checks for the support of the necessities for you or your family, as long as this do not imply that you have to compromise your faith in any way,) then you are not obligated to stay away from work and can safely work on Sundays as long as it is your last option. Below are some examples of acceptable reasons of why you can work on Sundays.
If you cannot continue home-schooling your children for example, this would be an acceptable reason with continuing to work on Sundays, another example would be if you had to move to a bad neighborhood with much drugs, violence or lasciviousness that would influence you or your family in a sinful way, or if by quitting your work, you may be forced to take another work that is sinful or immoral. This would be another reason to continue to work on Sundays until you have found another work where you are not forced to work on Sundays or forced to put your family's spiritual wellbeing in jeopardy.
This goes to say if the work you do is acceptable before God. If you sin against God by the specific work you do, such as selling contraception, porn, bad newspapers with immodest images or stories about sex or other sins etc, then you cannot go to that work even if you starve or don't have the means to support yourself or your family. In such cases you have to put your entire trust in God. You cannot be the cause of your brothers mortal sins without yourself being guilty of mortal sin!
“Therefore I say to you: Be not solicitous for your life, what you shall eat, nor for your body, what you shall put on. The life is more than the meat: and the body is more than the raiment... seek ye first the kingdom of God and his justice: and all these things shall be added unto you.” (Lk. 12:22-24, 27-28, 31)However, in the poorer countries where there is no chance of getting social welfare or income in any other way, it is totally acceptable to work on Sundays as long as the person must do it in order to survive. Many people do not operate under these conditions but work on Sundays in order to have more money than they need to survive. Yes, many people have the means necessary to stay away from work on Sundays, but only go to work to receive more abundance in riches. This is a clear mortal sin!
The following example on this can be seen clearer from St. Bridget's revelations, in the book rightly entitled the Book of Questions. It is composed of questions which Our Lord and Judge give wonderful answers to:
“Third question. Again the monk appeared on his ladder as before saying: "Why should I not exalt myself over others, seeing that I am rich?"
Answer to the third question. The Judge answered: "As to why you must not take pride in riches, I answer: The riches of the world only belong to you insofar as you need them for food and clothing. The world was made for this: that man, having sustenance for his body, might through work and humility return to me, his God, whom he scorned in his disobedience and neglected in his pride. However, if you claim that the temporal goods belong to you, I assure you that you are in effect forcibly usurping for yourself all that you possess beyond your needs. All temporal goods ought to belong to the community and be equally accessible to the needy out of charity.
You usurp for your own superfluous possession things that should be given to others out of compassion. However, many people do own much more than others but in a rational way, and they distribute it in discreet fashion. Therefore, in order not to be accused more severely at the judgment because you received more than others, it is advisable for you not to put yourself ahead of others by acting haughtily and hoarding possessions. As pleasant as it is in the world to have more temporal goods than others and to have them in abundance, it will likewise be terrible and painful beyond measure at the judgment not to have administered in reasonable fashion even licitly held goods."
http://www.catholic-saints.net/saints/st-bridget/st-bridget-of-sweden.php“The third commandment is that thou have mind and remember that thou hallow and keep holy thy Sabbath day or Sunday. That is to say, that thou shalt do no work nor operation on the Sunday or holy day, but thou shalt rest from all worldly labour and intend to prayer, and to serve God thy maker, which rested the seventh day of the works that he made in the six days before, in which he made and ordained the world. This commandment accomplish he that keep to his power the peace of his conscience for to serve God more holily. Then this day that the Jews called Sabbath is as much to say as rest. This commandment may no man keep spiritually that is encuмbered in his conscience with deadly sin, such a conscience can not be in rest nor in peace as long as he is in such a state. In the stead of the Sabbath day which was straightly kept in the old law, holy church hath established the Sunday in the new law. For our Lord arose from death to life on the Sunday, and therefore we ought to keep it holily, and be in rest from the works of the week before, and to cease of the work of sin, and to intend to do spiritual works, and to follow our Lord beseeching him of mercy and to thank him for his benefits, for they that break the Sunday and the other solemn feasts that be established to be hallowed in holy church, they sin deadly, for they do directly against the commandment of God aforesaid and holy church, but if it be for some necessity that holy church admitteth and granteth. But they sin much more then, that employ the Sunday and the feasts in sins, in lechery, in going to taverns in the service time, in gluttony and drinking drunk, and in other sins, outrages against God. For alas for sorrow I trow there is more sin committed on the Sunday and holy days and feasts than in the other work days. For then be they drunk, fight and slay, and be not occupied virtuously in God’s service as they ought to do. And as God command us to remember and have in mind to keep and hallow the holy day, they that so do sin deadly and observe and keep not this third commandment.” (From the Golden legend or the Lives of the Saints, volume 1, page 122-123)
From the above quote can be learned that man should not do the things on a Sunday as he would do on the other days. The Sunday is intended for God to be kept in holiness. Thus, if the only difference for you on Sundays is that you keep away from servile work, and do not give any of your time to God, what profit is there for you?
God commanded at least one day off for man so that man could rest from the world and use it for his spiritual well being, in praying, reading and doing other good works for the soul. You should thus spend the Sunday in abstaining from your own will, such as watching the tv, playing games, listening to music or the radio, etc, and instead strive to know God in solitude, prayer and meditation.
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