John Gill Commentary Exodus 12:51

"And it came to pass the selfsame day, that Jehovah did bring the children of Israel out of the land of Egypt by their hosts." — Exodus 12:51 (ASV)

And it came to pass the same day That the above ordinance was instituted and celebrated in the night: that the Lord brought the children of Israel out of the land of Egypt, by their armies ; by their several tribes, which were like so many armies, marching in large numbers, and with great order and regularity, (See Gill on Exodus 7:4).