CCC 1454 The reception of this sacrament ought to be prepared for by an examination of conscience made in the light of the Word of God. The passages best suited to this can be found in the Ten Commandments, the moral catechesis of the Gospels and the apostolic letters, such as the Sermon on the Mount and the apostolic teachings.1

CCC 1741 Liberation and salvation. By his glorious Cross Christ has won salvation for all men. He redeemed them from the sin that held them in bondage. “For freedom Christ has set us free.”2 In him we have communion with the “truth that makes us free.”3 The Holy Spirit has been given to us and, as the Apostle teaches, “Where the Spirit of the Lord is, there is freedom.”4 Already we glory in the “liberty of the children of God.”5

CCC 2515 Etymologically, “concupiscence” can refer to any intense form of human desire. Christian theology has given it a particular meaning: the movement of the sensitive appetite contrary to the operation of the human reason. The apostle St. Paul identifies it with the rebellion of the “flesh” against the “spirit.”6 Concupiscence stems from the disobedience of the first sin. It unsettles man’s moral faculties and, without being in itself an offense, inclines man to commit sins.7

CCC 2744 Prayer is a vital necessity. Proof from the contrary is no less convincing: if we do not allow the Spirit to lead us, we fall back into the slavery of sin.8 How can the Holy Spirit be our life if our heart is far from him?
Nothing is equal to prayer; for what is impossible it makes possible, what is difficult, easy. .. For it is impossible, utterly impossible, for the man who prays eagerly and invokes God ceaselessly ever to sin.9
Those who pray are certainly saved; those who do not pray are certainly damned.10

CCC 2819 “The kingdom of God [is] righteousness and peace and joy in the Holy Spirit.”11 The end-time in which we live is the age of the outpouring of the Spirit. Ever since Pentecost, a decisive battle has been joined between “the flesh” and the Spirit.12
Only a pure soul can boldly say: “Thy kingdom come.” One who has heard Paul say, “Let not sin therefore reign in your mortal bodies,” and has purified himself in action, thought and word will say to God: “Thy kingdom come!”13

1 Cf. Mt 5-7; Rom 12-15; 1 Cor 12-13; Gal 5; Eph 4-6; etc.
2 Gal 5:1.
3 Cf. In 8:32.
4 2 Cor 17.
5 Rom 8:21.
6 Cf. Gal 5:16, 17, 24; Eph 2:3.
7 Cf. Gen 3:11; Council of Trent: DS 1515.
8 Cf. Gal 5:16-25.
9 St. John Chrysostom, De Anna 4, 5: PG 54, 666.
10 St. Alphonsus Liguori, Del gran Mezzo della preghiera.
11 Rom 14:17.
12 Cf. Gal 5:16-25.
13 St. Cyril of Jerusalem, Catech. myst. 5, 13: PG 33, 1120A; cf. Rom 6:12.