Sign– this refers to the staff (of Moses): Moses’ staff was merely an instrument for the performance of the plagues and not a plague in and of itself. So why do we mention it here? According to the Midrash the ten plagues were engraved on Moses staff. According to the Ramban, they were engraved as Rabbi Yehudah’s abbreviation: d’tzakh adash bachav.¹⁹¹ Elsewhere we learn that the staff weighed 40 seah and was made of Sapphire into which the abbreviation of the plagues was engraved.¹⁹² The reason for this was so the Israelites would not say that without the plagues Israel could not have been redeemed. The staff proved that the plagues were part of a predestined plan. This is what we learn from the Torah: “I have hardened his heart and the hearts of his courtiers that I may display My signs among them…”¹⁹³ The plagues were engraved into the staff to show that God planned to carry them out in Egypt before the Israelites left. And because the staff was to be used for the splitting of the sea, Rabbi Yehudah’s abbreviation is mention following the recitation of the plagues.

footnotes: ¹⁹¹ Shemot Rabbah 5:6, also see Rambam ¹⁹² Yalkut Shimoni, section 173 ¹⁹³ Exodus 10:1