"For the Son of Man is Lord of the Sabbath."
The ultimate justification for the disciples’ violation of the sabbath rest is that Jesus, the Son of Man, has supreme authority over the law. Sunday is the 'Lord's Day'.
First three commandments of the Decalogue followed by the Catholic Church.
I
I am the LORD your God, who brought you out of the land of Egypt, out of the house of slavery. You shall not have other gods beside me. You shall not make for yourself an idol or a likeness of anything in the heavens above or on the earth below or in the waters beneath the earth; you shall not bow down before them or serve them. For I, the LORD, your God, am a jealous God, bringing punishment for their parents wickedness on the children of those who hate me, down to the third and fourth generation, but showing love down to the thousandth generation of those who love me and keep my commandments.
11
You shall not invoke the name of the LORD, your God, in vain. For the LORD will not leave unpunished anyone who invokes his name in vain.
III
Observe the sabbath day—keep it holy, as the LORD, your God, commanded you. 13Six days you may labor and do all your work, 14but the seventh day is a sabbath of the LORD your God. You shall not do any work, either you, your son or your daughter, your male or female slave, your ox or donkey or any work animal, or the resident alien within your gates, so that your male and female slave may rest as you do. Remember that you too were once slaves in the land of Egypt, and the LORD, your God, brought you out from there with a strong hand and outstretched arm. That is why the LORD, your God, has commanded you to observe the sabbath day.
IV
Honor your father and your mother, as the LORD, your God, has commanded you, that you may have a long life and that you may prosper in the land the LORD your God is giving you.
V
You shall not commit adultery.
VI
You shall not steal.
VII
You shall not bear dishonest witness against your neighbor.
VIII
You shall not covet your neighbor’s wife.
IX
You shall not covet your neighbor’s wife.
X
You shall not desire your neighbor’s house or field, his male or female slave, his ox or donkey, or anything that belongs to your neighbor.
Jews, Orthodox Christians, and most Protestants more closely follow the version of Exodus 20, while Catholics more closely follow the version of Deuteronomy 5. The main discrepancies come at the beginning and end of the lists of the Ten Commandments, as explained below:
http://www.catholic-resources.org/Bible/Decalogue.htm