Psalm 51, sometimes known as the miserere, has also been given the epithet ‘Psalm of Psalms’ by some. As I have studied it and reflected on its place in Church history over the last twelve months, or so, I am increasingly persuaded that such a claim might well be justified. The accolade owes something to its fundamental nature as arguably the purest and most profound plea for God’s mercy in all of Scripture. It also owes much to the psalm’s title and its reference to David’s double sins of adultery with Bathsheba and the murder of her husband Uriah—events that occupy 2 Samuel 11–12. This background to the psalm, and David’s confession to the Prophet Nathan also alluded to in the title, gave rise to the identification of this prayer as the penitential psalm par excellence. This recognition of Psalm 51 as chief of the seven penitential psalms was deemed appropriate not only because of its assumed dependence on the pivotal biblical narrative, but it also fittingly lies fourth, and so in the middle, of the sequence of Psalms 6, 32, 38, 51, 102, 130 and 143. It was also judged appropriate that in the Greek and Latin traditions that its identity as Psalm 50 could be conceived as a sort of a psalmic Jubilee.
It is possible that the identification of the seven penitential psalms originated with Augustine although the first extant identification of the specific seven, mentioned above, as belonging to a closed group is in Cassiodorus’ Explanation of the Psalms . In any case, Augustine’s sermon on Psalm 51 (50 in his Bible), in his Expositions of the Psalms , set the tone for exegesis of this psalm throughout the medieval period.
His sermon has often been neglected as a homily because Augustine reflects on its doctrinal contribution to what is generally termed original sin. But setting this aside and embracing Augustine as a faithful and earnest preacher proves to be a refreshing delight. The sermon comes across as a thrillingly tangible event despite more than 1,600 years lying between us and Augustine’s delivery (it was probably preached in the summer of 411). It comes to life in its early sentences as we hear him ask for quiet because his voice is struggling after preaching to a large gathering the previous day. We might well laugh as we note his acknowledgement of the preacher’s prevenient dilemma, the balance between saying enough to benefit a congregation but not so much as to ‘try its patience’. We also find out that the circus is in town and many congregants are absent and sampling its dubious pleasures.
Augustine sounds troubled that so many absentees will not hear his call to health that comes with repentance. He even urges those present to pass on the message to those that are not there. When it comes to the text he also sounds a little embarrassed to have to speak of the great King David as a sinner of some magnitude:
This woman Bathsheba was another man’s wife. We say this with grief and trepidation, yet since God wanted the matter to be written about, he does not mean us to hush it up. 
He must overcome his coyness because this psalm provides not only words of repentance but teaches too:
The story is not put before you as an example of falling, but as an example of rising again if you have fallen. Consider it carefully, so you do not fall. 
Augustine suggests that there might be two ways to hear of David’s immense sin. Firstly, his story might be misused as an exemplar of sin. Or secondly, and appropriately, as a as a warning to avoid sin by fleeing temptation. He is also at pains to point out that if any his congregation have already fallen into temptation and grave sin that they can still know forgiveness:
But if any who hear this have fallen already, and study the words of this psalm with some evil thing in their consciences, they must indeed be aware of the gravity of their wounds, but not despair of our noble physician. 
In this way, for Augustine this psalm carries a double grace, both as an exhortation to avoid sin and as a means to find the grace of Christ:
But as this psalm warns the fallen to be wary, so too it will not leave the fallen to despair. 
Augustine goes on to point to David as exemplar to those who have fallen into temptation:
Listen to him crying out, and cry out with him; listen to him groaning, and groan too; listen to him weeping, and add your tears to his; listen to him corrected, and share his joy. If sin could not be denied access to you, let the hope of forgiveness not be debarred. 
Anyone familiar with Augustine’s interpretative paradigm known as the totus Christus, that is the total Christ, might be surprised to hear how David eclipses Christ so completely in this homily. Elsewhere in his massive work on the Psalms he has no problem placing the words of sinners in Jesus’ mouth, for Christ can pray the words of his body the Church as well as words appropriate for him as Head of the Church. Augustine’s interpretation of Psalm 51 is an important reminder that Augustine is not a slave to one interpretative paradigm for the psalms. We can take comfort that the words of Psalm 51, though once David’s, can now be ours. In addition, when we pray them, in God’s mercy we can know the same bounteous grace that David experienced.
1. Cassiodorus, Explanation of the Psalms, three volumes, P. G. Walsh (translator), New York: Paulist Press, 1990.
2. Augustine, Expositions of the Psalms, six volumes, Maria Boulding (translator), John E. Rotelle (ed.), Hyde Park, New York: New City Press, 2000.
3. Expositions: Volume 2, p.411.
5. Expositions: Volume 2, p.413.
7. Expositions: Volume 2,p.414.