וישמע יתרו...כי הוציא ד' את ישראל ממצרים
Originally, Moshe Rabbeinu had taken his entire family with him to Egypt. Aharon HaKohen urged him to send them back to Midyan. His contention was very practical: The Jews in Egypt were already suffering; why should Moshe add to their number? Now, after hearing about all of the miracles, Yisro realized that the time had come for the family to be reunited. Chazal (Midrash Rabbah, Shemos 4:4) relate Moshe’s response to his brother’s admonishment. He said, “Tomorrow (in the near future), they (Klal Yisrael) will leave Egypt and stand at the foot of Har Sinai, where they will hear Hashem…