“And it came to pass at midnight.” Here the record changes from instruction to historical event. Exodus 12:1-28 had occurred before the 10^th of Nisan (the first month) and were instructions of what Israel was to do: select a lamb or goat on the 10^th (Exod. 12:3, 5), kill it on the 14^th and put the blood on the doorposts (Exod. 12:6-7), and Yahweh would pass through on the 15^th (Exod. 12:12; the 15^th started at sunset). Exodus 12:29 switches to the 15^th of Nisan and Yahweh moving powerfully against Egypt.

“midnight.” The Passover Lamb was killed on the 14^th of Nisan, and at sunset the 14^th changed to the 15^th, (the Jewish day started at sunset, in most of the Western World the day starts at midnight) so the Israelites left Egypt on the 15^th of Nisan. The 15^th of the lunar month was always a full moon, so the Israelites had plenty of light to travel by when they left that night.