Some Arabic manuscripts of the “Psalms of David” contain not the Biblical Psalms but Muslim compositions that sound more like the Qur’an: not human praises and prayers to God, but God’s admonitions to the prophet David, urging him to flee the pleasures of this world, spend his nights in repentant prayer, and prepare for the Day of Judgment. There are echoes of the Biblical Psalms and Gospels, but the ethos is markedly different: rather than the Psalmist’s plaintive laments or grandiose descriptions of creation, one hears God thundering his own majesty and warning of the fires of hell. This alternative scripture exists in at least ten different versions, all stemming from a single eighth- or ninth-century collection of one hundred psalms composed by a member of an early Muslim ascetic movement that was inspired in part by Christian monasticism. Only a small fragment of that text has been preserved in its original form, but the entire text was edited, rewritten, rearranged, and expanded by several later editors who modified it to fit their own views. For example, the original text referred without blushing to the Biblical story of David’s adultery with Bathsheba and murder of Uriah, but most later editors omitted or minimized David’s sin out of respect for his status as a prophet. Over the centuries Muslims have treasured and recopied these psalms for several reasons, including their predictions of Muhammad and their occasional polemics against Christians, but they were intended mainly as a critique of worldly Muslims. In their original form they reflect a time when Muslims and Christians had contrasting notions of scripture but held overlapping views about religious piety, which they expressed using a shared vocabulary of stories and ideas: the figure of David, his Psalms and his sins, virtue and repentance, asceticism and spirituality, heaven and hell, and a rich common stock of maxims and metaphors.