The Book of Psalms has been the prayer book of the Church for centuries, the six Penitential Psalms being especially relevant during Lent.
Psalm 6 (Penitential)
O Lord, do not rebuke me in Your anger, Nor chasten me in Your hot displeasure. Have mercy on me, O Lord, for I am weak; O Lord, heal me, for my bones are troubled.
My soul also is greatly troubled; But You, O Lord-how long? Return, O Lord, deliver me! Oh, save me for Your mercies' sake! For in death there is no remembrance of You; In the grave who will give You thanks?
I am weary with my groaning; All night I make my bed swim; I drench my couch with my tears. My eye wastes away because of grief; It grows old because of all my enemies. Depart from me, all you workers of iniquity;
For the Lord has heard the voice of my weeping. The Lord has heard my supplication; The Lord will receive my prayer. Let all my enemies be ashamed and greatly troubled. Let them turn back and be ashamed suddenly.
Psalm 32 (Penitential)
Blessed is he whose transgression is forgiven, Whose sin is covered. Blessed is the man to whom the Lord does not impute iniquity,And in whose spirit there is no deceit.
When I kept silent, my bones grew old Through my groaning all the day long. For day and night Your hand was heavy upon me; My vitality was turned into the drought of summer.
I acknowledged my sin to You, And my iniquity I have not hidden. I said, "I will confess my transgressions to the Lord," And You forgave the iniquity of my sin.
For this cause everyone who is godly shall pray to You In a time when You may be found; Surely in a flood of great waters They shall not come near him. You are my hiding place; You shall preserve me from trouble; You shall surround me with songs of deliverance.
I will instruct you and teach you in the way you should go; I will guide you with My eye. Do not be like the horse or like the mule, Which have no understanding, Which must be harnessed with bit and bridle, Else they will not come near you. Many sorrows shall be to the wicked;
But he who trusts in the Lord, mercy shall surround him. Be glad in the Lord and rejoice, you righteous; And shout for joy, all you upright in heart!
Psalm 38:1-4, 8-12, 21-22 (Penitential)
O Lord, do not rebuke me in Your wrath, Nor chasten me in Your hot displeasure! For Your arrows pierce me deeply, And Your hand presses me down.
There is no soundness in my flesh Because of Your anger, nor any health in my bones Because of my sin.
For my iniquities have gone over my head; Like a heavy burden they are too heavy for me. I am feeble and severely broken; I groan because of the turmoil of my heart.
Lord, all my desire is before You; And my sighing is not hidden from You. My heart pants, my strength fails me; As for the light of my eyes, it also has gone from me.
My loved ones and my friends stand aloof from my plague, And my relatives stand afar off. Those also who seek my life lay snares for me; Those who seek my hurt speak of destruction, and plan deception all the day long……Do not forsake me, O Lord; O my God, be not far from me!
Make haste to help me, O Lord, my salvation!
Psalm 51:1-2,10-12 (Penitential)
Have mercy upon me, O God, According to Your lovingkindness; According to the multitude of Your tender mercies, Blot out my transgressions.
Wash me thoroughly from my iniquity, and cleanse me from my sin.Create in me a pure heart, O God, and renew a steadfast spirit within me.
Do not cast me from your presence or take your Holy Spirit from me. Restore to me the joy of your salvation and grant me a willing spirit, to sustain me.
Psalm 130:1-6 (Penitential)
Out of the depths I have cried to You, O Lord; Lord, hear my voice! Let Your ears be attentive To the voice of my supplications.
If You, Lord, should mark iniquities, O Lord, who could stand? But there is forgiveness with You, That You may be feared.
I wait for the Lord, my soul waits, And in His word I do hope.
My soul waits for the Lord More than those who watch for the morning-Yes, more than those who watch for the morning.
Psalm 143 (Penitential)
Hear my prayer, O Lord, Give ear to my supplications! In Your faithfulness answer me, And in Your righteousness, Do not enter into judgment with Your servant,
For in Your sight no one living is righteous. For the enemy has persecuted my soul; He has crushed my life to the ground; He has made me dwell in darkness, Like those who have long been dead.
I meditate on all Your works; I muse on the work of Your hands. I spread out my hands to You; My soul longs for You like a thirsty land. Answer me speedily, O Lord; My spirit fails!
Do not hide Your face from me, Lest I be like those who go down into the pit. Cause me to hear Your lovingkindness in the morning, For in You do I trust; Cause me to know the way in which I should walk, For I lift up my soul to You.