The 'Passing the River' alphabet (Transitus Fluvii, 'the passage of the river') is one of three magical alphabets published by Heinrich Cornelius Agrippa in Book III of his Three Books of Occult Philosophy (1533). Its name alludes to the crossing of the Euphrates by the exiles of Israel; its twenty-two letters correspond one-to-one to the Hebrew alphabet, and it was used in Renaissance ceremonial magic for inscribing divine and angelic names. This letter is the Passing the River form of the Hebrew letter Zayin, whose name means 'sword or weapon' and whose gematria value is 7. Its meaning and numerical value are inherited from that Hebrew correspondence; the script is a set of glyph-forms for the Hebrew letters, not an independent alphabet with its own separate symbolism. Its name, Transitus Fluvii, crossing the river, evokes Israel's exiles passing the Euphrates, attaching a sixteenth-century invention to a biblical setting.
Agrippa printed Celestial, Malachim and Passing the River together in Book III of the Three Books of Occult Philosophy, Cologne 1533, without naming a source, and no earlier witness to any of the three survives; historians read them as a Christian kabbalist's own reworking of Hebrew letters, most likely Agrippa's, following Reuchlin's Rhineland work opening Hebrew letter mysticism to Christian scholars a generation before.
Occultism today largely sets the three scripts aside as a documented ancient language, treating them as a Renaissance invention. In the Sefer Yetzirah's own threefold division of the alphabet, Zayin is one of the twelve simple letters, assigned in the text's scheme to a zodiac sign, a month and a bodily faculty, though which sign fits which letter is not recorded and the order is disputed.