Despite the centrality of the shahāda to the Islamic faith, very little work has been done on investigating the origins and nature of this concept in early Islam. Particularly striking in this regard is the lack of attention given to the frequent appearances of the root sh-h-d throughout the Quran, which appear in deeply significant theological contexts. In this paper, we argue that the Quran engages closely with the biblical subtext of the covenantal oath structure in its frequent references to the act of shahāda or “bearing witness.” By employing an inner-Quranic and intertextual analysis, we demonstrate that when the Quran uses variations of the root sh-h-d in a theological context this clearly indicates the taking of an oath, or the imposition of an oath, through which individuals or communities enter into a covenant with Allah. The Quran here follows clear precedents in biblical literature which developed a standard formula by which the Israelites affirm their fealty to God. The Quran develops this further, however, by turning it into a structure of authority that commands or imposes this oath onto other people, thus dividing the mechanism of the covenantal oath into two complementary parts. In doing so, the Quran reveals its deep engagement with the biblical theme of the covenantal oath by developing a systematic vocabulary which expands the mechanism of the covenantal undertaking into an entire theological structure embedded at the very heart of its revelatory message.