A careful analysis of the relationship between Mandaean sources and Jewish, Christian, Islamic and other Gnostic literature is long overdue. If the older view that the Mandaeans originated among the followers of John the Baptist has rightly come to be seen as problematic, the suggestion that it was only the much later context of the Islamic period which provided the primary impetus for focusing on the figure of John the Baptist also faces serious difficulties. The proposed paper will offer a close examination of the relationship between chapter 18 of the Mandaean Book of John, which focuses on portents of the birth of John the Baptist and the reaction of his father Zechariah to them, and those traditions (including but not limited to the Lukan infancy narrative) on which the author appears to have drawn, and with which he or she appears to have been in dialogue. Evidence of polemical interaction with Christianity and Islam notwithstanding, the central features of this particular story– which includes references to the Torah and the Merkabah – strongly suggest that it was Judaism which provided the principal formative matrix for the creative Mandaean reworking of these stories.