From what would John’s immersions purify? Considering texts from the Synoptics, Josephus, and 1QS on purification, sin, and forgiveness, various options are outlined and disentangled with the help of conceptual metaphor theory, especially conceptual blending, and the theory of ritual form. Although John’s immersion was a ritual innovation, broadening ritual purification to include the removal of offensive acts and a change of behaviour by a physical water ritual, a conceptual blending analysis speaks strongly against immersion as a substitute for sacrifice and questions any confusion in relation to the priestly purity system. The theory of ritual form suggests an infrequent and high-arousal Special Agent ritual. Features reminiscent of pre-Hasmonean practices (river and ‘wilderness’ rather than miqveh), gave John’s rite a sense of genuineness and divine agency, making it attractive and emotionally satisfying. The eschatological setting of general purification in view of a divine encounter further contributed to the ritual’s success.