CIC 226 It means making good use of created things: faith in God, the only One, leads us to use everything that is not God only insofar as it brings us closer to him, and to detach ourselves from it insofar as it turns us away from him:
My Lord and my God, take from me everything that distances me from you.
My Lord and my God, give me everything that brings me closer to you.
My Lord and my God, detach me from myself to give my all to you.1

CIC 577 At the beginning of the Sermon on the Mount Jesus issued a solemn warning in which he presented God’s law, given on Sinai during the first covenant, in light of the grace of the New Covenant:
Do not think that I have come to abolish the law or the prophets: I have come not to abolish but to fulfill. For truly I tell you, until heaven and earth pass away, not one letter, not one stroke of a letter, will pass from the law, until all is accomplished. Therefore, whoever breaks one of the least of these commandments, and teaches others to do the same, will be called least in the kingdom of heaven; but whoever does them and teaches them will be called great in the kingdom of heaven.2

CIC 581 The Jewish people and their spiritual leaders viewed Jesus as a rabbi.3 He often argued within the framework of rabbinical interpretation of the Law.4 Yet Jesus could not help but offend the teachers of the Law, for he was not content to propose his interpretation alongside theirs but taught the people “as one who had authority, and not as their scribes”.5 In Jesus, the same Word of God that had resounded on Mount Sinai to give the written Law to Moses, made itself heard anew on the Mount of the Beatitudes.6 Jesus did not abolish the Law but fulfilled it by giving its ultimate interpretation in a divine way: “You have heard that it was said to the men of old. .. But I say to you. ..”7 With this same divine authority, he disavowed certain human traditions of the Pharisees that were “making void the word of God”.8

CIC 678 Following in the steps of the prophets and John the Baptist, Jesus announced the judgment of the Last Day in his preaching.9 Then will the conduct of each one and the secrets of hearts be brought to light.10 Then will the culpable unbelief that counted the offer of God’s grace as nothing be condemned.11 Our attitude to our neighbor will disclose acceptance or refusal of grace and divine love.12 On the Last Day Jesus will say: “Truly I say to you, as you did it to one of the least of these my brethren, you did it to me.”13

CIC 1034 Jesus often speaks of “Gehenna” of “the unquenchable fire” reserved for those who to the end of their lives refuse to believe and be converted, where both soul and body can be lost.14 Jesus solemnly proclaims that he “will send his angels, and they will gather. .. all evil doers, and throw them into the furnace of fire,”15 and that he will pronounce the condemnation: “Depart from me, you cursed, into the eternal fire!”16

CIC 1424 It is called the sacrament of confession, since the disclosure or confession of sins to a priest is an essential element of this sacrament. In a profound sense it is also a “confession” – acknowledgment and praise – of the holiness of God and of his mercy toward sinful man.
It is called the sacrament of forgiveness, since by the priest’s sacramental absolution God grants the penitent “pardon and peace.”17
It is called the sacrament of Reconciliation, because it imparts to the sinner the live of God who reconciles: “Be reconciled to God.”18 He who lives by God’s merciful love is ready to respond to the Lord’s call: “Go; first be reconciled to your brother.”19

CIC 1456 Confession to a priest is an essential part of the sacrament of Penance: “All mortal sins of which penitents after a diligent self-examination are conscious must be recounted by them in confession, even if they are most secret and have been committed against the last two precepts of the Decalogue; for these sins sometimes wound the soul more grievously and are more dangerous than those which are committed openly.”20
When Christ’s faithful strive to confess all the sins that they can remember, they undoubtedly place all of them before the divine mercy for pardon. But those who fail to do so and knowingly withhold some, place nothing before the divine goodness for remission through the mediation of the priest, “for if the sick person is too ashamed to show his wound to the doctor, the medicine cannot heal what it does not know.”21

CIC 1967 The Law of the Gospel “fulfills,” refines, surpasses, and leads the Old Law to its perfection.22 In the Beatitudes, the New Law fulfills the divine promises by elevating and orienting them toward the “kingdom of heaven.” It is addressed to those open to accepting this new hope with faith – the poor, the humble, the afflicted, the pure of heart, those persecuted on account of Christ and so marks out the surprising ways of the Kingdom.

CIC 2053 To this first reply Jesus adds a second: “If you would be perfect, go, sell what you possess and give to the poor, and you will have treasure in heaven; and come, follow me.”23 This reply does not do away with the first: following Jesus Christ involves keeping the Commandments. The Law has not been abolished,24 but rather man is invited to rediscover it in the person of his Master who is its perfect fulfillment. In the three synoptic Gospels, Jesus’ call to the rich young man to follow him, in the obedience of a disciple and in the observance of the Commandments, is joined to the call to poverty and chastity.25 The evangelical counsels are inseparable from the Commandments.

CIC 2142 The second commandment prescribes respect for the Lord’s name. Like the first commandment, it belongs to the virtue of religion and more particularly it governs our use of speech in sacred matters.

CIC 2153 In the Sermon on the Mount, Jesus explained the second commandment: “You have heard that it was said to the men of old, ‘You shall not swear falsely, but shall perform to the Lord what you have sworn.’ But I say to you, Do not swear at all. .. Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from the evil one.”26 Jesus teaches that every oath involves a reference to God and that God’s presence and his truth must be honored in all speech. Discretion in calling upon God is allied with a respectful awareness of his presence, which all our assertions either witness to or mock.

CIC 2258 “Human life is sacred because from its beginning it involves the creative action of God and it remains for ever in a special relationship with the Creator, who is its sole end. God alone is the Lord of life from its beginning until its end: no one can under any circumstance claim for himself the right directly to destroy an innocent human being.”27

CIC 2262 In the Sermon on the Mount, the Lord recalls the commandment, “You shall not kill,”28 and adds to it the proscription of anger, hatred, and vengeance. Going further, Christ asks his disciples to turn the other cheek, to love their enemies.29 He did not defend himself and told Peter to leave his sword in its sheath.30

CIC 2302 By recalling the commandment, “You shall not kill,”31 our Lord asked for peace of heart and denounced murderous anger and hatred as immoral.
Anger is a desire for revenge. “To desire vengeance in order to do evil to someone who should be punished is illicit,” but it is praiseworthy to impose restitution “to correct vices and maintain justice.”32 If anger reaches the point of a deliberate desire to kill or seriously wound a neighbor, it is gravely against charity; it is a mortal sin. The Lord says, “Everyone who is angry with his brother shall be liable to judgment.”33

CIC 2331 “God is love and in himself he lives a mystery of personal loving communion. Creating the human race in his own image. .. God inscribed in the humanity of man and woman the vocation, and thus the capacity and responsibility, of love and communion.”34
“God created man in his own image. .. male and female he created them”;35 He blessed them and said, “Be fruitful and multiply”;36 “When God created man, he made him in the likeness of God. Male and female he created them, and he blessed them and named them Man when they were created.”37

CIC 2336 Jesus came to restore creation to the purity of its origins. In the Sermon on the Mount, he interprets God’s plan strictly: “You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that every one who looks at a woman lustfully has already committed adultery with her in his heart.”38 What God has joined together, let not man put asunder.39
The tradition of the Church has understood the sixth commandment as encompassing the whole of human sexuality.

CIC 2338 The chaste person maintains the integrity of the powers of life and love placed in him. This integrity ensures the unity of the person; it is opposed to any behavior that would impair it. It tolerates neither a double life nor duplicity in speech.40

CIC 2380 Adultery refers to marital infidelity. When two partners, of whom at least one is married to another party, have sexual relations – even transient ones – they commit adultery. Christ condemns even adultery of mere desire.41 The sixth commandment and the New Testament forbid adultery absolutely.42 The prophets denounce the gravity of adultery; they see it as an image of the sin of idolatry.43

CIC 2382 The Lord Jesus insisted on the original intention of the Creator who willed that marriage be indissoluble.44 He abrogates the accommodations that had slipped into the old Law.45
Between the baptized, “a ratified and consummated marriage cannot be dissolved by any human power or for any reason other than death.”46

CIC 2464 The eighth commandment forbids misrepresenting the truth in our relations with others. This moral prescription flows from the vocation of the holy people to bear witness to their God who is the truth and wills the truth. Offenses against the truth express by word or deed a refusal to commit oneself to moral uprightness: they are fundamental infidelities to God and, in this sense, they undermine the foundations of the covenant.

CIC 2466 In Jesus Christ, the whole of God’s truth has been made manifest. “Full of grace and truth,” he came as the “light of the world,” he is the Truth.47 “Whoever believes in me may not remain in darkness.”48 The disciple of Jesus continues in his word so as to know “the truth [that] will make you free” and that sanctifies.49 To follow Jesus is to live in “the Spirit of truth,” whom the Father sends in his name and who leads “into all the truth.”50 To his disciples Jesus teaches the unconditional love of truth: “Let what you say be simply ‘Yes or No.’”51

CIC 2514 St. John distinguishes three kinds of covetousness or concupiscence: lust of the flesh, lust of the eyes, and pride of life.52 In the Catholic catechetical tradition, the ninth commandment forbids carnal concupiscence; the tenth forbids coveting another’s goods.

CIC 2608 From the Sermon on the Mount onwards, Jesus insists on conversion of heart: reconciliation with one’s brother before presenting an offering on the altar, love of enemies, and prayer for persecutors, prayer to the Father in secret, not heaping up empty phrases, prayerful forgiveness from the depths of the heart, purity of heart, and seeking the Kingdom before all else.53 This filial conversion is entirely directed to the Father.

CIC 2792 Finally, if we pray the Our Father sincerely, we leave individualism behind, because the love that we receive frees us from it. The “our” at the beginning of the Lord’s Prayer, like the “us” of the last four petitions, excludes no one. If we are to say it truthfully, our divisions and oppositions have to be overcome.54

CIC 2841 This petition is so important that it is the only one to which the Lord returns and which he develops explicitly in the Sermon on the Mount.55 This crucial requirement of the covenant mystery is impossible for man. But “with God all things are possible.”56

CIC 2845 There is no limit or measure to this essentially divine forgiveness,57 whether one speaks of “sins” as in Luke (11:4), “debts” as in Matthew (6:12). We are always debtors: “Owe no one anything, except to love one another.”58 The communion of the Holy Trinity is the source and criterion of truth in every relation ship. It is lived out in prayer, above all in the Eucharist.59
God does not accept the sacrifice of a sower of disunion, but commands that he depart from the altar so that he may first be reconciled with his brother. For God can be appeased only by prayers that make peace. To God, the better offering is peace, brotherly concord, and a people made one in the unity of the Father, Son, and Holy Spirit.60

1 St. Nicholas of Flue; cf. Mt 5:29-30; 16:24-26.
2 Mt 5:17-19.
3 Cf Jn 11:28; 3:2; Mt 22:23-24, 34-36.
4 Cf. Mt 12:5; 9:12; Mk 2:23-27; Lk 6:6-g; Jn 7:22-23.
5 Mt 7:28-29.
6 Cf. Mt 5:1.
7 Mt 5:33-34.
8 Mk 7:13; cf. 3:8.
9 Cf. Dan 7:10; Joel 3-4; Mal 3: 19; Mt 3:7-12.
10 Cf Mk 12:38-40; Lk 12:1-3; Jn 3:20-21; Rom 2:16; I Cor 4:5.
11 Cf. Mt 11:20-24; 12:41-42.
12 Cf. Mt 5:22; 7:1-5.
13 Mt 25:40.
14 Cf. Mt 5:22, 29; 10:28; 13:42, 50; Mk 9:43-48.
15 Mt 13:41-42.
16 Mt 25:41.
17 OP 46 formula of absolution.
18 2 Cor 5:20.
19 MT 5:24.
20 Council of Trent (1551): DS 1680 (ND 1626); cf. Ex 20:17; Mt 5:28.
21 Council of Trent (1551): DS 1680 (ND 1626); cf. St. Jerome, In Eccl. 10, 11: PL 23:1096.
22 Cf. Mt 5:17-19.
23 Mt 19:21.
24 Cf. Mt 5:17.
25 Cf. Mt 19:6-12, 21, 23-29.
26 Mt 5:33-34,37; Cf. Jas 5:12.
27 CDF, instruction, Donum vitae, intro. 5.
28 Mt 5:21.
29 Cf. Mt 5:22-39; 5:44.
30 Cf. Mt 26:52.
31 Mt 5:21.
32 St. Thomas Aquinas, STh II-II, 158, 1 ad 3.
33 Mt 5:22.
34 FC 11.
35 Gen 1:27.
36 Gen 1:28.
37 Gen 5:1-2.
38 Mt 5:27-28.
39 Cf. Mt 19:6.
40 Cf. Mt 5:37.
41 Cf. Mt 5:27-28.
42 Cf. Mt 5:32; 19:6; Mk 10:11; 1 Cor 6:9-10.
43 Cf. Hos 2:7; Jer 5:7; 13:27.
44 Cf. Mt 5:31-32; 19:3-9; Mk 10 9; Lk 16:18; 1 Cor 7:10-ll.
45 Cf. Mt 19:7-9.
46 CIC, can. 1141.
47 Jn 1:14; 8:12; Cf. 14:6.
48 Jn 12:46.
49 Jn 8:32; Cf. 17:17.
50 Jn 16:13.
51 Mt 5:37.
52 Cf. 1 Jn 2:16.
53 Cf. Mt 5:23-24, 44-45; 6:7,14-15, 21, 25, 33.
54 Cf. Mt 5:23-24; 6:14-15.
55 Cf. Mt 6:14-15; 5:23-24; Mk 11:25.
56 Mt 19:26.
57 Cf. Mt 18:21-22; Lk 17:3-4.
58 Rom 13:8.
59 Cf. Mt 5:23-24; 1 Jn 3:19-24.
60 St. Cyprian, De Dom. orat. 23: PL 4, 535-536; cf. Mt 5:24.