At the end of the 430 years, on the very day, all the regiments of the Lord went out of the land of Egypt.

And on this very day the Lord brought the Israelites out of the land of Egypt by their regiments.

So you will keep the Feast of Unleavened Bread, because on this very day I brought your regiments out from the land of Egypt, and so you must keep this day perpetually as a lasting ordinance.