The Ash Wednesday prayer below, like so many used in liturgical worship, is based on centuries-old texts. It expresses the basic themes of a worship that prepares the people to journey into the death of Jesus:

Almighty and everlasting God, you hate nothing you have made and forgive the sins of all who are penitent: Create and make in us new and contrite hearts, that we, worthily lamenting our sins and acknowledging our wretchedness, may obtain of you, the God of all mercy, perfect remission and forgiveness; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, for ever and ever. Amen.

These passages are commonly used for an Ash Wednesday service. All passages are from the ESV:

Joel 2:1–2, 12–17

Blow a trumpet in Zion;

                  sound an alarm on my holy mountain!

Let all the inhabitants of the land tremble,

                  for the day of the Lord is coming; it is near,

                  a day of darkness and gloom,

                  a day of clouds and thick darkness!

Like blackness there is spread upon the mountains

                  a great and powerful people;

their like has never been before,

                  nor will be again after them

                  through the years of all generations.

“Yet even now,” declares the Lord,

                  “return to me with all your heart,

with fasting, with weeping, and with mourning;

                  and rend your hearts and not your garments.”

Return to the Lord your God,

                  for he is gracious and merciful,

slow to anger, and abounding in steadfast love;

                  and he relents over disaster.

Who knows whether he will not turn and relent,

                  and leave a blessing behind him,

a grain offering and a drink offering

                  for the Lord your God?

Blow the trumpet in Zion;

                  consecrate a fast;

call a solemn assembly;

                  gather the people.

Consecrate the congregation;

                  assemble the elders;

gather the children,

                  even nursing infants.

Let the bridegroom leave his room,

                  and the bride her chamber.

Between the vestibule and the altar

                  let the priests, the ministers of the Lord, weep

and say, “Spare your people, O Lord,

                  and make not your heritage a reproach,

                  a byword among the nations.

Why should they say among the peoples,

                  ‘Where is their God?’”

Isaiah 58:1–12

“Cry aloud; do not hold back;

                  lift up your voice like a trumpet;

declare to my people their transgression,

                  to the house of Jacob their sins.

Yet they seek me daily

                  and delight to know my ways,

as if they were a nation that did righteousness

                  and did not forsake the judgment of their God;

they ask of me righteous judgments;

                  they delight to draw near to God.

‘Why have we fasted, and you see it not?

                  Why have we humbled ourselves, and you take no knowledge of it?’

Behold, in the day of your fast you seek your own pleasure,

                  and oppress all your workers.

Behold, you fast only to quarrel and to fight

                  and to hit with a wicked fist.

Fasting like yours this day

                  will not make your voice to be heard on high.

Is such the fast that I choose,

                  a day for a person to humble himself?

Is it to bow down his head like a reed,

                  and to spread sackcloth and ashes under him?

Will you call this a fast,

                  and a day acceptable to the Lord?

“Is not this the fast that I choose:

                  to loose the bonds of wickedness,

                  to undo the straps of the yoke,

to let the oppressed[b] go free,

                  and to break every yoke?

Is it not to share your bread with the hungry

                  and bring the homeless poor into your house;

when you see the naked, to cover him,

                  and not to hide yourself from your own flesh?

Then shall your light break forth like the dawn,

                  and your healing shall spring up speedily;

your righteousness shall go before you;

                  the glory of the Lord shall be your rear guard.

Then you shall call, and the Lord will answer;

                  you shall cry, and he will say, ‘Here I am.’

If you take away the yoke from your midst,

                  the pointing of the finger, and speaking wickedness,

if you pour yourself out for the hungry

                  and satisfy the desire of the afflicted,

then shall your light rise in the darkness

                  and your gloom be as the noonday.

And the Lord will guide you continually

                  and satisfy your desire in scorched places

                  and make your bones strong;

and you shall be like a watered garden,

                  like a spring of water,

                  whose waters do not fail.

And your ancient ruins shall be rebuilt;

                  you shall raise up the foundations of many generations;

you shall be called the repairer of the breach,

                  the restorer of streets to dwell in.

2 Corinthians 5:20b–6:10

God making his appeal through us. We implore you on behalf of Christ, be reconciled to God. For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God. Working together with him, then, we appeal to you not to receive the grace of God in vain. For he says, “In a favorable time I listened to you, and in a day of salvation I have helped you.” Behold, now is the favorable time; behold, now is the day of salvation. We put no obstacle in anyone’s way, so that no fault may be found with our ministry, but as servants of God we commend ourselves in every way: by great endurance, in afflictions, hardships, calamities, beatings, imprisonments, riots, labors, sleepless nights, hunger; by purity, knowledge, patience, kindness, the Holy Spirit, genuine love; by truthful speech, and the power of God; with the weapons of righteousness for the right hand and for the left; through honor and dishonor, through slander and praise. We are treated as impostors, and yet are true; as unknown, and yet well known; as dying, and behold, we live; as punished, and yet not killed; as sorrowful, yet always rejoicing; as poor, yet making many rich; as having nothing, yet possessing everything.

Matthew 6:16-21

And when you fast, do not look gloomy like the hypocrites, for they disfigure their faces that their fasting may be seen by others. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by others but by your Father who is in secret. And your Father who sees in secret will reward you. Do not lay up for yourselves treasures on earth, where moth and rust destroy and where thieves break in and steal, but lay up for yourselves treasures in heaven, where neither moth nor rust destroys and where thieves do not break in and steal. For where your treasure is, there your heart will be also.