Contemporary suspicion abounds against thinkers from the classical through the early modern period who draw on supposed metaphysical notions of impersonal and ahistorical substance to frame, and in the minds of critics undermine, discussions of God and the human being. Careful examinations into the actual use of substance from the classical through the early modern period can tell a different story, which is epitomized in Augustine and Luther’s exegesis of Psalm 68/9. In the midst of his treatment of this Psalm, Augustine takes up the received philosophical notion of substance and critically reinterprets it within a trinitarian and christological framework. For Augustine, substance is imbued with a twofold—creative and soteriological—receptive dynamic toward God that is fulfilled within the loving movement of human praise toward God. Working within this Augustinian reading, Luther also rejects what he terms the philosophical approach to substance in favor of a christological reading that extends and expands on aspects of Augustine’s account of the relational and dynamic nature of substance. Here Luther moves the concept of substance more explicitly from a metaphysical to an existential context, arguing that substance refers to the qualities of human life rather than to what constitutes the basis of life. Luther also more explicitly draws out the manner in which the historical and soteriological space of human existence defines the nature of human substance, harkening closer to Heidegger’s being-in than to the temporally flat, ahistorical notions of substance the Augustinian tradition is often accused of incorporating into its anthropology.