Numbers 5:23

The priest shall write these curses in a book, &c.— The Jews call every scroll, whereon any thing is written, ספר sepher, a book; and the rabbis tell us, that these maledictions were written upon vellum or parchment: but Calmet observes, that it is far from certain that parchment was used for writing in the time of Moses, or many ages after; and the original word often signifies tablets of plain wood, or covered over with wax, which was the most ancient manner of writing; see his dissertation Sur les Livres Anciens. These curses, wrote thus, most probably in wax, were to be wiped off at or into the bitter water, אלאּמי el-mei; so that the woman was, as it were, to drink the curse itself. It is plain that the jealousy-offering was made before the woman drank the water, Numbers 5:26.