CIC 208 Faced with God’s fascinating and mysterious presence, man discovers his own insignificance. Before the burning bush, Moses takes off his sandals and veils his face in the presence of God’s holiness.1 Before the glory of the thrice-holy God, Isaiah cries out: “Woe is me! I am lost; for I am a man of unclean lips.”2 Before the divine signs wrought by Jesus, Peter exclaims: “Depart from me, for I am a sinful man, O Lord.”3 But because God is holy, he can forgive the man who realizes that he is a sinner before him: “I will not execute my fierce anger. .. for I am God and not man, the Holy One in your midst.”4 The apostle John says likewise: “We shall. .. reassure our hearts before him whenever our hearts condemn us; for God is greater than our hearts, and he knows everything.”5

CIC 1781 Conscience enables one to assume responsibility for the acts performed. If man commits evil, the just judgment of conscience can remain within him as the witness to the universal truth of the good, at the same time as the evil of his particular choice. The verdict of the judgment of conscience remains a pledge of hope and mercy. In attesting to the fault committed, it calls to mind the forgiveness that must be asked, the good that must still be practiced, and the virtue that must be constantly cultivated with the grace of God:
We shall. .. reassure our hearts before him whenever our hearts condemn us; for God is greater than our hearts, and he knows everything.6

CIC 2631 The first movement of the prayer of petition is asking forgiveness, like the tax collector in the parable: “God, be merciful to me a sinner!”7 It is a prerequisite for righteous and pure prayer. A trusting humility brings us back into the light of communion between the Father and his Son Jesus Christ and with one another, so that “we receive from him whatever we ask.”8 Asking forgiveness is the prerequisite for both the Eucharistic liturgy and personal prayer.

CIC 2778 This power of the Spirit who introduces us to the Lord’s Prayer is expressed in the liturgies of East and of West by the beautiful, characteristically Christian expression: parrhesia, straightforward simplicity, filial trust, joyous assurance, humble boldness, the certainty of being loved.9

CIC 2822 Our Father “desires all men to be saved and to come to the knowledge of the truth.”10 He “is forbearing toward you, not wishing that any should perish.”11 His commandment is “that you love one another; even as I have loved you, that you also love one another.”12 This commandment summarizes all the others and expresses his entire will.

CIC 2845 There is no limit or measure to this essentially divine forgiveness,13 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.”14 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.15
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.16

1 Cf. EX 3:5-6.
2 Is 6:5.
3 Lk 5:8.
4 Hos 11:9.
5 I Jn 3:19-20.
6 1 Jn 3:19-20.
7 Lk 18:13.
8 1 Jn 3:22; cf. 1:7-2:2.
9 Cf. Eph 3:12; Heb 3:6; 4:16; 10:19; 1 Jn 2:28; 3:21; 5:14.
10 1 Tim 2:3-4.
11 2 Pet 3:9; cf. Mt 18:14.
12 Jn 13:34; cf. 1 Jn 3; 4; Lk 10:25-37.
13 Cf. Mt 18:21-22; Lk 17:3-4.
14 Rom 13:8.
15 Cf. Mt 5:23-24; 1 Jn 3:19-24.
16 St. Cyprian, De Dom. orat. 23: PL 4, 535-536; cf. Mt 5:24.