"Vayasa Moshe". Why did Moshe need to force Yisrael to travel?
Rashi: Because the Egyptians adorned their horses with gold and silver ornaments and with precious stones, 1 which Yisrael found in the sea and were busy collecting. 2
Refer to 15:9:151:2.
Rashi: Because the booty of the sea exceeded that of Egypt, as the Pasuk hints in Shir ha'Shirim, 1:11. (Everyone left Egypt with ninety laden donkeys. How could they take more than this from what was on the horses? This is in order according to the opinion that there were fifteen humdred Egyptians for each Yisrael - Refer to 14:7:2:3*. Or if the booty of the sea (silver, gold and gems) was worth more than that of Egypt, which was mostly clothing. - PF
Why did the people complain about not having water only after three days?
Targum Yonasan, Da'as Zekenim #1, Hadar Zekenim and Rosh: 'Water' refers to Torah 1 (Mitzvos - Targum Yonasan). After three days without Torah, they rebelled. 2
Da'as Zekenim #2: Because they took water from Egypt, and after three days it ran out. 3
Bava Kama, 82a: As the Pasuk writes in Yeshayah, 55:1 "Hoy Kol Tzamei L'chu la'Mayim". See Torah Temimah, note 34 DH 'Vedarshu'.
Bav Kama: That is why the Chachamim enacted to read the Torah on Monday, Thursday and Shabbos, so that three days should not pass without Torah. See Torah Temimah, note 34, who elaborates.
