It use to be that stores were closed on Sunday but now there are few stores that are not open. This gives Christians the temptation to misuse the Lord’s day.
The main scripture verse on keeping a day of rest is in (Deuteronomy 5:12-14)
"Observe the Sabbath day by keeping it holy, as the LORD your God has commanded you. Six days you shall labor and do all your work, but the seventh day is a Sabbath to the LORD your God. On it you shall not do any work, neither you, nor your son or daughter, nor your manservant or maidservant, nor your ox, your donkey or any of your animals, nor the alien within your gates, so that your manservant and maidservant may rest, as you do."
The Jews in the old testament were very strict on keeping the Sabbath day command as shown in (Num 15:32-35) While the people of Israel were in the wilderness, they found a man gathering sticks on the Sabbath day. And those who found him gathering sticks brought him to Moses and Aaron and to all the congregation. They put him in custody, because it had not been made clear what should be done to him. And the LORD said to Moses,” The man shall be put to death; all the congregation shall stone him with stones outside the camp."
They did not buy or sell on this day of rest as shown in (Nehemiah 10:31).
“As for the peoples of the land who bring wares or any grain on the sabbath day to sell, we will
not buy from them on the sabbath or a holy day; and we will forego the crops the seventh year and the exaction of every debt”
Now Jesus clarifies that it is lawful to do good on this day of rest as shown in (Mt 12:11-13) He said to them, "If any of you has a sheep and it falls into a pit on the Sabbath, will you not take hold of it and lift it out? How much more valuable is a man than a sheep! Therefore it is lawful to do good on the Sabbath." Then he said to the man, "Stretch out your hand." So he stretched it out and it was completely restored, just as sound as the other.
Now they will say “what’s the big deal if I go shopping on Sunday. I am doing something I enjoy and I am not working.” No you are not working but you are making someone else work and not keep the Lord’s Day. They may reply "well that person is going to be working at the store whether I go shopping or not." That is right but when you go you are participating in their working. The reason why they are working is enough people were misusing the Lord’s Day. If enough people kept the command it wouldn’t pay for them to be working on Sunday and the store would close.
Now there are exceptions to shopping on Sunday. If there is a serious need to get medicine or food then that is ok. Another example could be people who happen to be traveling. They may need to eat at a restaurant on Sunday. Firefighters may need to work on Sunday as well as people in the emergency room. One other aspect of keeping the Lord’s Day is communal worship.
Heb 10:24-25 "And let us consider how we may spur one another on toward love and good deeds. Let us not give up meeting together, as some are in the habit of doing, but let us encourage one another—and all the more as you see the Day approaching."
This next scripture verse pertains to celebrating the Passover in the Old Testament and how if someone fails to celebrate it he is cut off.
Num 9:13 But if a man who is ceremonially clean and not on a journey fails to celebrate the Passover, that person must be cut off from his people because he did not present the Lord’s offering at the appointed time. That man will bear the consequences of his sin.
The Mass is the New Testament fulfillment of the Passover. Jesus is our Passover lamb. In the Old Testament the Jews who celebrated the Passover had to eat the lamb and the unleavened bread to celebrate the Passover (Ex 12:3-4). God told them that this would be and ordinance lasting forever (Ex 12:17). When God says forever he means it. Jesus fulfilling this he becomes the Passover lamb. At Mass we have unleavened bread that becomes the Lamb of God. The one in the same sacrifice of Jesus on Calvary re presented. It is not a new sacrifice but the same one. When the sun rises every morning it is not a new sun but a re presentation of the same sun. The greek word used in the last supper for this memorial sacrifice is anamnesis. Jesus’ sacrifice which transcends time and space is what makes this possible. So now you go back to the verse in Numbers about being cut off for not celebrating the Passover and apply it to its fulfillment. The antitype is always greater than the type. For example the antitype baptism is greater than the type circumcision. The antitype Mary ark of the new covenant is greater than the type the box ark of the old covenant.
When the Catholic Church says it is a mortal sin (serious sin which is acted upon with full knowledge and full consent of the will) to miss Mass, it speaks with the authority of Jesus. Jesus gave his authority first to Peter in Mt 16:18 in which he gives him the keys of the kingdom and authority to bind things on earth that will be bound in heaven. Jesus then gives it to the apostles in Mt 18:18 and this authority was passed on to every Catholic Bishop after the apostles through the laying on of hands. Jesus explains in Lk 10:16 that if you reject the Church leaders you reject him. John also reiterates this in 1 Jn 4:6 and says “We are of God. Whoever knows God listens to us, and he who is not of God does not listen to us. By this we know the spirit of truth and the spirit of error.” There are a few excuses that can allow for missing of mass. Being sick, bad weather, in a situation that it is impossible to get to Mass. Vacation is not an excuse. God doesn’t take vacations. You can go to masstimes.org to find Churches when you travel. Going to a protestant church does not fulfill Sunday obligation because it is not the worship Jesus instructed at the last supper and it is not a re presentation of Jesus’ sacrifice.
Sunday is a day for worship primarily. Secondly to rest from work. It is a day for prayer, spiritual reading and meditation. It is a day for the family to spend time with each other. If you go shopping on Sunday the person working at the cash register is pulled away from these things.