The only psalm that is prescribed to be recited in its entirety at every Divine Liturgy is (in the Orthodox Old Testament) Psalm 50 (Psalm 51 in the Hebrew text). During the Cherubic Hymn, just before the Great Entrance when the gifts of bread and wine are brought to the altar as the Church prepares for the Holy Oblation, the priest censes the altar, the sanctuary and the people, and quietly recites the psalm (and is expected to know it by heart): “Have mercy on me, O God, in accordance with your great mercy…” The priest recites the psalm up until verse 17: “A sacrifice to God is a broken spirit; a broken and a humbled heart God will not despise”, and concludes the psalm after the solemn procession with the holy gifts when he places the bread and wine upon the altar: “Do good to Sion, Lord, in your good pleasure; and let the walls of Jerusalem be rebuilt. Then you will be well pleased with a sacrifice of righteousness, oblation and whole burnt offerings. Then they will offer calves upon your altar”.
It is within this liturgical context that I should like to examine this remarkable prayer of repentance.
Psalm 50 was written by the Prophet King David after he acknowledged and confessed his sin before the Prophet Nathan (2 Samuel 12). David’s sin was a terrible two-fold sin. He committed adultery with Bathsheba, the wife of Uriah the Hittite. Bathsheba became pregnant and David sent for Uriah, who was with the Israelite army at the siege of Rabbah, so that he may lie with his wife and conceal the identity of the child’s father. Uriah refused to do so while his companions were in the field of battle and David sent him back to Joab, the commander, with a message instructing him to abandon Uriah on the battlefield, “that he may be struck down, and die.”
It is therefore the prayer of a murderer and adulterer that the celebrant of the Liturgy recites (and makes his own in prayer) as he prepares for the Holy Oblation. For sin lies not only in our actions, but also in the corruption and evil desires of the heart. Indeed, if the priest has actually committed murder or adultery, he is, according to canon law, to be defrocked and can not celebrate the Liturgy at all. And yet the priest is here expected to identify himself with a murderer and adulterer – murder and adultery being two of the most grievous sins against God and man. In His sermon on the mount, our Lord states: ‘You have heard that it was said, “Do not commit adultery”. But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.’ (Matt. 5:27-28). In the case of murder, St Basil the Great and St John Chrysostom put it very strongly to the rich in regard to helping the poor, claiming that those who refuse to share with others in time of urgent need, when starvation and disease pose an immanent threat to human life, may be accounted guilty of murder. As St Basil writes in the homily, In Time of Famine and Drought, “Whoever has the ability to remedy the suffering of others, but chooses rather to withhold aid out of selfish motives, may properly be judged the equivalent of a murderer.” And St John Chrysostom, in his Homily on 1 Thessalonians, states that he who denies alms to the starving is as much his brother’s murderer as was Cain.
While the priest recites the psalm, the choir chants the Cherubic Hymn: “We who in a mystery represent the cherubim and sing the thrice-holy hymn to the life-giving Trinity, let us now lay aside every care of this life. For we are about to receive the King of all….” In laying aside our worldly concerns, we are also to lay down before God our sins, to ‘cast our troubles on the Lord’ (Psalm 54:22), and having thus unburdened our hearts we may offer the Holy Oblation in peace. This applies not only to the clergy but to the whole congregation. For it is the clergy and people together who are to offer the Holy Oblation, and not the clergy alone. But it is the priest’s particular cross to bear, his special calling and service to the Church, to take on the sins of the people as his own and to bring them before God and ask for His mercy. This is made clear in the prayers of the clergy at the Divine Liturgy: “…enable us to offer you gifts and spiritual sacrifices for our sins and those committed in ignorance by the people…”
At the Great Entrance, we are not far from hearing the hymn of the Seraphim, which the Prophet Isaiah and the beloved disciple John heard (Isaiah 6:1, Rev. 4:8): “Holy, holy, holy, Lord of hosts; heaven and earth are full of your glory…” And our response to this holiness is that of Isaiah: “Woe to me! I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the Lord Almighty”. Our sense of sinfulness does not come from measuring the distance between our conduct and some sort of morality or law; it is only in the presence of God Himself, the only Holy One, that we come to know how sinful we are. And, indeed, in that moment we feel like murderers and adulterers. For the deeper we enter into the infinite holiness and presence of God, the more sinful we feel by comparison. This is why we identify with a murderer and adulterer in Psalm 50.
The psalm is not merely an expression of penitence and self-disgust. It is the overwhelming holiness of God that is the source of profound repentance, and it is particularly related to the coming of the Holy Spirit. The recitation of Psalm 50 is a preparation for the epiclesis, when we call on the Holy Spirit to change the bread and wine into Christ’s Body and Blood. And so in Psalm 50 the priest says, “Create a clean heart in me, O God, and renew a right Spirit within me. Do not cast me out from your presence, and do not take your Holy Spirit from me.” In the Liturgy of St Basil the Great, the priest prays that God will not, because of his own sins, “withhold the grace of the Holy Spirit from the Gifts here spread forth”.
It is because of this sense of being in the presence of holiness that Psalm 50 is far from being morbid and morose. We are reminded that repentance finds its fulfilment not in looking back on our sins in despair, but in looking forward with hope and faith; not in looking down into the pits of hell, but in looking up to God in heaven. We are called to become what God wants us to be: holy. God says to His people: ‘Be holy, because I am holy’ (Lev. 11:44). And St Peter writes, ‘just as he who called you is holy, so be holy in all you do’, and goes on to quote Leviticus: ‘for it is written: “Be holy, because I am holy”.’ (1 Peter 1:15-16). St Paul calls the Christians ‘holy ones’ or ‘saints’ (ἅγιοι). We are reminded of this calling to be holy just before Communion when the priest elevates the Body of Christ and exclaims: “the Holy Things for the holy”.
Psalm 50 is a prayer not of despair but of hope: “You will sprinkle me with hyssop and I shall be cleansed. You will wash me and I shall be made whiter than snow. You will make me hear of joy and gladness; the bones which have been humbled will rejoice… Give me back the joy of your salvation, and establish me with your sovereign Spirit. I will teach transgressors your ways, and sinners will turn to you again…”. And we are reminded that God hears the prayer and contrition of the heart: “if you had wanted a sacrifice, I would have given it. You will not take pleasure in burnt offerings. A sacrifice to God is a broken spirit; a broken and a humbled heart God will not despise”.
Thus, as the Liturgy of the Faithful begins, we are to unburden our hearts in confession before God as we lay aside every care of this life, that we may “Stand with awe…stand with fear” and “pay heed to the Holy Oblation, that we may offer…. mercy and peace: a sacrifice of praise”. Apart from humility of heart, God desires mercy and peace from us. That is the sacrifice God asks of us. But to offer this, we must acknowledge first that we have fallen short of God’s mercy and peace. We must turn to God in repentance, put aside all hatred and animosity, all pride and injustice, and be reconciled with one another. For we cannot offer mercy and peace if we have none. Without love, peace and humility, our Liturgy is not acceptable to God. The Prophet Isaiah puts it very strongly: “What do I care for the number of your sacrifices? says the Lord. I have had enough of whole-burnt rams and fat of fatlings. I take no pleasure in the blood of calves, lambs and goats. When you come in to visit me, who asks these things of you? Trample my courts no more! Bring no more worthless offerings; your incense is loathsome to me. New moon and sabbath, calling of assemblies, octaves with wickedness: I cannot bear them. I detest your new moons and festivals; they weigh me down, I am tired of the load. When you spread out your hands, I close my eyes to you. Though you pray even more, I will not listen. Your hands are full of blood! Wash yourselves clean! Put away your misdeeds from before my eyes; stop doing evil; learn to do good. Make justice your aim: redress the wronged, hear the orphan’s plea, defend the widow.” (Isaiah 1:11-17)
This is why the celebrant of the Liturgy, identifying himself with the worst of sinners, prays for God’s mercy for himself and for the people as the Church begins to prepare for the Holy Oblation and to receive Christ in Holy Communion: “Wash me thoroughly from my wickedness, and cleanse me from my sin… Turn away your face from my sins and blot out all my iniquities. Create a clean heart in me, O God, and renew a right Spirit within me”. For only when we are at peace – with God, with one another, and with ourselves – can we worthily offer our liturgy to God and, in so doing, be made worthy to receive the Body and Blood of Christ for the forgiveness of sins and eternal life. Then ‘we will hear of joy and gladness; the bones which have been humbled will rejoice’, and we can return to the world to ‘tell what great things God has done for us’ (Luke 8:38). And being thus filled with that divine joy and gladness, we can “teach transgressors your ways, and sinners will turn to you again”.
Have mercy on me, O God, in accordance with your great mercy. According to the multitude of your compassion blot out my offence. Wash me thoroughly from my wickedness, and cleanse me from my sin. For I acknowledge my wickedness, and my sin is ever before me. Against you alone I have sinned and done what is evil in your sight, that you may be justified in your words and win when you are judged. For see, in wickedness I was conceived and in sin my mother bore me. For see, you have loved truth; you have shown me the hidden and secret things of your wisdom. You will sprinkle me with hyssop and I shall be cleansed. You will wash me and I shall be made whiter than snow. You will make me hear of joy and gladness; the bones which have been humbled will rejoice. Turn away your face from my sins and blot out all my iniquities. Create a clean heart in me, O God, and renew a right Spirit within me. Do not cast me out from your presence, and do not take your Holy Spirit from me. Give me back the joy of your salvation, and establish me with your sovereign Spirit. I will teach transgressors your ways, and sinners will turn to you again. O God, the God of my salvation, deliver me from bloodshed and my tongue will rejoice at your justice. Lord, you will open my lips, and my mouth will proclaim your praise. For if you had wanted a sacrifice, I would have given it. You will not take pleasure in burnt offerings. A sacrifice to God is a broken spirit; a broken and a humbled heart God will not despise. Do good to Sion, Lord, in your good pleasure; and let the walls of Jerusalem be rebuilt. Then you will be well pleased with a sacrifice of righteousness, oblation and whole burnt offerings. Then they will offer calves upon your altar.
Source: Archdiocese of Thyateira and Great Britain
 The Orthodox Old Testament is the Ancient Greek translation known as the Septuagint (LXX). It was translated in stages between the 3rd and 2nd centuries B.C. and was used by the Jews of the Dispersion. It was the Christian Old Testament since the 1st century A.D.
 The numbering of the psalms diverges after psalm 8 and re-converges from psalm 148, as follows:
114 116 v.1-9
115 116 v.10-19
146 147 v.1-11
147 147 v.12-20
*Though contained in the earliest extant manuscripts of the Septuagint, Psalm 151 is not regarded in the Church as equal to the other 150 psalms, designated as ἔξωθεν τοῦ ἀριθμοῦ “outside the number” and is never read in church.