Many a theological statement has been deduced from alleged changes to the text of the Septuagint by the author of Hebrews. These deductions do not always keep in mind the different textual traditions of the Septuagint text. This article points out the relevance of determining the Vorlage of Hebrews before making such comparisons. This is done by using the quotation of LXX Ps 39:7-9 in Heb 10:5b-7 as an example. By means of textual criticism, the most probable Vorlage of LXX Ps 39:7-9 and the text of Heb 10:5b-7 is established. Thereafter, a comparison is made between these two texts. Differences between the texts are pointed out and shown to be intentional changes introduced by the author. In doing so, the theological meaning behind these changes is brought to the fore.