Catholic Morality begins with the 10 commandments.
Ex. 20:2 aI am the LORD your God, who brought you out of the land of Egypt,bout of the house of slavery. 3 You shall not have other gods beside me.*4 You shall not make for yourself an idolcor a likeness of anything*in the heavens above or on the earth below or in the waters beneath the earth; 5 you shall not bow down before them or serve them.dFor I, the LORD, your God, am a jealous God, inflicting punishment for their ancestors’ wickedness on the children of those who hate me, down to the third and fourth generation*; 6 but showing love down to the thousandth generation of those who love me and keep my commandments.
Ex. 20:7 You shall not invoke the name of the LORD, your God, in vain.*eFor the LORD will not leave unpunished anyone who invokes his name in vain.
Ex. 20:8 Remember the sabbath day—keep it holy.*9 Six days you may labor and do all your work, 10but the seventh day is a sabbath of the LORD your God.fYou shall not do any work, either you, your son or your daughter, your male or female slave, your work animal, or the resident alien within your gates. 11For in six days the LORD made the heavens and the earth, the sea and all that is in them; but on the seventh day he rested.gThat is why the LORD has blessed the sabbath day and made it holy.*
Ex. 20:12 *hHonor your father and your mother, that you may have a long life in the land the LORD your God is giving you.i
Ex. 20:13 You shall not kill.*j
Ex. 20:14 You shall not commit adultery.k
Ex. 20:15 You shall not steal.l
Ex. 20:16 You shall not bear false witness against your neighbor.m
Ex. 20:17 You shall not covet your neighbor’s house. You shall not covet your neighbor’s wife, his male or female slave, his ox or donkey, or anything that belongs to your neighbor.n
The account of Jesus and the young prince tells the limits of legalism.
Matt. 19:16 hNow someone approached him and said, “Teacher, what good must I do to gain eternal life?”*17He answered him, “Why do you ask me about the good? There is only One who is good.*If you wish to enter into life, keep the commandments.” 18*iHe asked him, “Which ones?” And Jesus replied, “ ‘You shall not kill; you shall not commit adultery; you shall not steal; you shall not bear false witness; 19honor your father and your mother’; and ‘you shall love your neighbor as yourself.’” 20*The young man said to him, “All of these I have observed. What do I still lack?” 21jJesus said to him, “If you wish to be perfect,*go, sell what you have and give to [the] poor, and you will have treasure in heaven. Then come, follow me.” 22When the young man heard this statement, he went away sad, for he had many possessions.
Jesus expands on the Old Law in the Sermon on the Mount.
Jesus begins with the beatitudes:
Math 5:3-12
“Blessed are the poor in spirit,*
for theirs is the kingdom of heaven.a
4 *Blessed are they who mourn,b
for they will be comforted.
5 *Blessed are the meek,c
for they will inherit the land.
6 Blessed are they who hunger and thirst for righteousness,*
for they will be satisfied.
7 Blessed are the merciful,
for they will be shown mercy.d
8 *Blessed are the clean of heart,e
for they will see God.
9 Blessed are the peacemakers,
for they will be called children of God.
10 Blessed are they who are persecuted for the sake of righteousness,*
for theirs is the kingdom of heaven.f
11Blessed are you when they insult you and persecute you and utter every kind of evil against you [falsely] because of me.g12*Rejoice and be glad, for your reward will be great in heaven.hThus they persecuted the prophets who were before you.
The Beatitudes are counterintuitive running opposite to the world’s view of happiness–lead a self-determined life, freely choosing and self-actualizing your desires.
Then Jesus says that we are not to live by the letter of the law, but by the spirit behind the law.
Matt. 5:17*“Do not think that I have come to abolish the law or the prophets. I have come not to abolish but to fulfill. 18Amen, I say to you, until heaven and earth pass away, not the smallest letter or the smallest part of a letter will pass from the law, until all things have taken place.m19Therefore, whoever breaks one of the least of these commandments and teaches others to do so will be called least in the kingdom of heaven. But whoever obeys and teaches these commandments will be called greatest in the kingdom of heaven.*20I tell you, unless your righteousness surpasses that of the scribes and Pharisees, you will not enter into the kingdom of heaven.
Matt. 5:21 “You have heard that it was said to your ancestors,n‘You shall not kill; and whoever kills will be liable to judgment.’*22*But I say to you, whoever is angry*with his brother will be liable to judgment,oand whoever says to his brother, ‘Raqa,’ will be answerable to the Sanhedrin, and whoever says, ‘You fool,’ will be liable to fiery Gehenna. 23Therefore, if you bring your gift to the altar, and there recall that your brother has anything against you,p24leave your gift there at the altar, go first and be reconciled with your brother, and then come and offer your gift. 25Settle with your opponent quickly while on the way to court with him.qOtherwise your opponent will hand you over to the judge, and the judge will hand you over to the guard, and you will be thrown into prison. 26Amen, I say to you, you will not be released until you have paid the last penny. 27*“You have heard that it was said,r‘You shall not commit adultery.’ 28But I say to you, everyone who looks at a woman with lust has already committed adultery with her in his heart. 29*If your right eye causes you to sin, tear it out and throw it away.sIt is better for you to lose one of your members than to have your whole body thrown into Gehenna. 30And if your right hand causes you to sin, cut it off and throw it away. It is better for you to lose one of your members than to have your whole body go into Gehenna. 31*“It was also said, ‘Whoever divorces his wife must give her a bill of divorce.’t32But I say to you, whoever divorces his wife (unless the marriage is unlawful) causes her to commit adultery, and whoever marries a divorced woman commits adultery.u33*v“Again you have heard that it was said to your ancestors, ‘Do not take a false oath, but make good to the Lord all that you vow.’ 34wBut I say to you, do not swear at all;*not by heaven, for it is God’s throne; 35nor by the earth, for it is his footstool; nor by Jerusalem, for it is the city of the great King. 36Do not swear by your head, for you cannot make a single hair white or black. 37*Let your ‘Yes’ mean ‘Yes,’ and your ‘No’ mean ‘No.’ Anything more is from the evil one. 38*“You have heard that it was said,x‘An eye for an eye and a tooth for a tooth.’ 39yBut I say to you, offer no resistance to one who is evil. When someone strikes you on [your] right cheek, turn the other one to him as well. 40If anyone wants to go to law with you over your tunic, hand him your cloak as well. 41Should anyone press you into service for one mile,*go with him for two miles.z42Give to the one who asks of you, and do not turn your back on one who wants to borrow.a
Matt. 5:43 b“You have heard that it was said, ‘You shall love your neighbor and hate your enemy.’c44But I say to you, love your enemies, and pray for those who persecute you, 45that you may be children of your heavenly Father, for he makes his sun rise on the bad and the good, and causes rain to fall on the just and the unjust. 46For if you love those who love you, what recompense will you have? Do not the tax collectors*do the same? 47And if you greet your brothers only, what is unusual about that? Do not the pagans do the same?*48So be perfect,*just as your heavenly Father is perfect.
In short Jesus is calling us to a morality based on love and grace, and to live as our Heavenly Father would have us live.