The Book of Exodus, chapter 20, tells how God on Mt. Sinai revealed to Moses the Ten Commandments (also called the Decalogue) giving them to him on two stone tablets. In Deuteronomy 5 Moses is pictured as telling all the people the Ten Commandments. Exodus 32:15 describes how God Himself gave Moses the two stone tablets which He had made. Moses broke them in anger when he saw the people had fallen into idolatry; in chapter 34 Moses cuts two more tablets to replace the ones he had broken.

There is some difference in grouping the commandments, and hence in numbering, between the more usual Protestant and the Catholic lists of the commandments. The sense is the same.

Some have doubted if these laws could have been transmitted orally so many centuries. We reply: We do not know the date of the Exodus, and therefore, of the law; but the chief suggestions are about 1290 B.C. (under Rameses II) or around 1450 B.C. (perhaps under Thutmose III). In either case, writing was known before that time in Egypt and in Mesopotamia. We have the Law Code of Hammurabi — his dates are uncertain, perhaps about 1792-50 BC. His Code has 282 laws, some of them quite similar to those of the Ten Commandments, though the first four commandments of the Decalogue seem to be unique to the Hebrews. Further, oral transmission in ancient times was remarkable. Thus for long the name of King Tudiya, first king of Assyria, was considered only a legend. But now tablets have been found at Ebla, showing a treaty between King Ebrum of Ebla, and King Tudiya, dating from about 2350 B.C., about 13 centuries before the Assyrian King lists were written down (Cf. G. Pettinato, The Archives of Ebla, Doubleday, N. Y. 1981, pp. 70, 73, 103-05). These ten commandments are simply the code of basic morality. Our Lord accepted them and said He came not to destroy but to fulfill. He also perfected them, making them broader in some things (Matthew 5:17-48). And He summed them up in the two commandments of love of God and of neighbor. The Old Testament had the first, love of God (Deuteronomy 5:4-5). It had the second, in a way (Leviticus 19:18), but the Jews understood neighbor to mean only fellow countrymen. Our Lord extended the word neighbor, in the parable of the good Samaritan, to mean all humans. (Let us recall here what we said in speaking of Moses in our opening sketch of salvation history, and of the relation of the words of St. Paul to those of Jesus).

God cannot gain anything by our obedience. But He wants us to obey for two reasons: 

1) Moral goodness requires that creatures obey their Creator. He, being
   Holiness itself,  loves all that is good; 
2) He wants to give us good things; His commandments tell us how to be
   open to receive   His gifts, and how to avoid the penalties built into the
   nature of things (since sinful things   are contrary to our nature, and so are
   harmful to us).

In accord with this, the Old Testament says that the law is wisdom. It is that. In Deuteronomy 4:6 Moses tells the people that if they obey the law, other nations will say: "This great nation is really a wise and understanding people." The Jews carried this idea to such lengths that the Palestinian Targum on Deuteronomy 32:4 asserts that God Himself spends three hours a day studying the law!

The First commandment: "I am the Lord your God, you shall not have other gods before me"

The commandment most directly prohibits the worship of false gods, and, to follow up, prohibits images. The Jews were very prone to such idolatry before the great exile. Afterwards they seem to have been largely healed.

The prohibition of images does not apply now, since the danger of idolatry has gone. Our images of Our Lord, His Mother, and the Saints, are just helps to devotion. We do not adore them. We only venerate them, but even the veneration goes not to the image but to the holy one for which the image stands.

We need to avoid also superstition, which is offering worship in an improper manner, probably based on false revelations, e. g, prayers that if said for a set number of days will have an infallible result. Vain observance would be magic or satanism. Sadly, there is explicit worship of satan today. The Ouija board is dangerous, and we should avoid it, since part of its results come from automatic writing, but often enough satan intervenes.

We must also avoid sacrilege, which is scornful treatment of a person, place or thing dedicated to God. To receive Holy Communion in the state of sin is sacrilege. We avoid also simony, which takes its name from Simon Magus, who tried to buy with money the gift of working miracles . St. Peter rebuked him strongly (Acts 8:9-24). To give a stipend for a Mass etc. is not simony. It is not buying the Mass, it is an offering for the support of the priest, or a means of sharing specially in the Mass.

In a loose sense, not a strict sense, some people today "worship" the false gods of secularism, which says this world is the only one to be considered, or hedonism, which makes pleasure the goal of life, or Communism, which denies the existence of God, seeks happiness in a so-called classless society in Russia the very opposite has been true, great privilege and luxury for the ruling class.

On the positive side, we are to worship God, which means most essentially, adoration and obedience. Adoration means recognizing who He is, and who I am in comparison. This is due in justice, but also, more importantly, in love: we recognize that God is not only infinitely good to us, but also in Himself. As such we should respond by pleasing Him by making ourselves open to receive His gifts — for that pleases Him. that is what love for God means. In no other way to we really give Him anything. The central virtue that gave all its value to the sacrifice of Jesus was His obedience to the will of the Father. Without it, His death would have been a tragedy, not a redemption.

Sacrifice for us (some pagan peoples had different ideas of sacrifice) has an external sign, which is there to express and perhaps even promote the essential, which is the interior dispositions. God complained through Isaiah (Is 29:13: "This people draw near to me with their mouth, and honor me with their lips, but their heart is far from me." The ancient Israelites at that time seemed to think their participation in their liturgy meant merely making responses and singing — these things were good, but the obedience was lacking. We must join our obedience — carried out in the recent past, or to come in the near future — to the offering of Jesus, when, through the human priest, He puts Himself on the altar under the appearance of separation of body and blood, to express His continued attitude of obedience to the Father. So catechists say our role in the Mass is ACTS:
adoration,
contrition, 
thanksgiving, and 
supplication. 
We should do these things, but we must not let them cause us to forget the real center is obedience (Cf. Romans 519 and LG #3).

Outside the time of the sacrifice of the Mass, we should of course pray. Regular times are called for to insure we do not forget prayer altogether.

To God we give adoration, it the sense just described; but to Our Lady and the Saints we give only veneration, honor, something less than adoration. The sacrifice of Jesus is infinite, and so in a way we should need to do nothing. Yet St. Paul insists that the whole Christian regime means we are saved and made holy if and to the extent that we are not only members of Christ, but like Him. That includes being like Him in the work of reparation for sin (cf. Rom 8:17-18; Col 1. 24).

Second Commandment: "You shall not take the name of the Lord your God in vain."

1. Blasphemy and cursing

The chief thing prohibited by this commandment is taking the name of God in vain, i.e., using it in and empty way. Ordinarily this will not be more than venial sin, but it should be avoided. The Jews in the last centuries before Christ would not pronounce the word Yahweh even in prayer. Instead they said Lord.

Blasphemy means any speech, thought or action that shows contempt for God. It is very grave. The Old Testament called for the death penalty (Leviticus 24:16).

When someone confesses cursing and swearing, it usually means neither thing. He means using damn or hell, or vulgar four letter words dealing with the results of elimination. These things are very rude, and mark a person as low class. But, unless someone really wishes evil to another, they are not sinful at all.

A vow is a promise made to God to do something better than what is obligatory. A vow imposes a real obligation. Deuteronomy 23:22 warns us not to make a vow and then not keep it. Whether or not mortal sin is involved depends on the importance of the thing vowed.

To take an oath is to call God to witness that what one says is true. It is lawful to do so, if there is sufficient reason.

To make a false oath is perjury. It offends against God's truthfulness, since it calls Him to witness to a lie. Proverbs 19:9 says one who does that will not go without punishment.

An adjuration is the solemn use of the name of God to strengthen a command. This is permissible if done with the right intention, and in cases where such a thing is really called for.

Third Commandment: "Remember to keep holy the Lord's day."

1. Sundays and Holy Days: Mass Obligation

In Old Testament times, this commandment required keeping the Sabbath (Saturday), holy and a day of rest. The day was moved to Sunday by the authority Christ gave to His Church, to commemorate the Resurrection of Our Lord and Pentecost Sunday, when the Holy Spirit came upon the Apostles. The latest Code of Canon Law restates this obligation for us: there are false reports there is no longer an obligation.

Our participation in the Mass must be most of all interior, joining our obedience to the Father to that of Jesus. At the Last Supper He used the seeming separation of body and bloody (by bread and wine) to stand for death, and He thereby said to the Father that He would obey His command to die. The Mass repeats hat He did through the ministry of a human priest. The obedience of the Heart of Jesus on our altars is a continuation of the obedience in which He died. One way to carry out our part would be to spend a few minutes before each Mass, to see what one has done in obeying the Father since the last Mass. If well done, this can be presented along with the obedience of Jesus at the double consecration. If some things are not well done, regrets are called for. One can also look ahead to the time soon to come to see: is something coming soon in which I know the will of the Father? Then: Do I mean to do it? This too can be joined to the obedience of Christ. The external things, making responses, singing etc. are very good, but not the essentials of participation.

Of course, grave reason can excuse one from Sunday Mass, e.g., physical impossibility, sufficient sickness, great difficulty of getting to Mass, or the need to care for the baby or sick relatives, when no one else can take these duties over at the time.

Besides Sunday, we must take part in Mass on Holy Days of obligation. In the United States these are: 

January 1 (Solemnity of Mary the Mother of God), 
Ascension Thursday (40 days after Easter), 
Assumption (August 15) , 
All Saints Day (November 1), 
Immaculate Conception (December 8), and 
Christmas (December 25).

Sunday as a Day of Rest

In the New Code of Canon Law, the Church has revised this obligation, in Canon 1247: "They must also keep from such work or business as would inhibit the worship to be given to God, the joy proper to the Lord's day, and the due relaxation of mind and body."

There is much latitude given, but to merely do all day on Sunday the same job one does all week would surely be wrong. Sunday ought to be a day that is special and different to a considerable extent.