if we are to appreciate the way Scripture uses Scripture to prove a doctrinal point, then we must appreciate the larger hermeneutical frameworks within which citations are employed, the original (historical and literary) contexts within which proof-texts are found, and we must also possess a certain canonical sensitivity to how biblical motifs and themes unfold in the history of redemption, and, perhaps most importantly, how Christ is understood to be the climax of that unfolding historical development.
The quotation of a biblical passage in the Summa [Theologiae] is meant to point the reader to a commentary written by Thomas or to an exegetical tradition of which he and the intelligent reader would be aware.A proof-text is, in modern parlance, a hypertext.
The Summa covers a wider terrain than any one biblical commentary—in fact, it could be characterized as a whole-Bible commentary with its very structure being shaped by what we now call “biblical theology.” The particular biblical commentaries contain more detailed expositions of pertinent passages that are merely referenced offhand or quoted briefly in the Summa. For example, he discusses the equality of power of the Father and of the Son in two types of texts (ST 1a.42.6 and in his Commentary on John 5:19). In the article in the ST, Thomas mentions a number of other texts in John’s Gospel (5:20; 5:30; 14:31), and he makes reference to no patristic sources. When you trace those references or quotations to his commentary, however, you see extended analysis of a deep patristic tradition.