But on the day before the people went out of Egypt, being as yet unacquainted with dates, they were instructed by the command of God to acknowledge that month which was then passing by as the first of all months; and were told that the sacrifice of the day was to be solemnly and regularly offered in coming ages, so that, on the fourteenth day of the month, a lamb without blemish, one year old, should be slain as a victim, and that the door-posts should be sprinkled with its blood; that its flesh was wholly to be eaten, but not a bone of it was to be broken; that they should abstain from what was leavened for seven days, using only unleavened bread; and that they should hand down the observance to their posterity.
Thus the people went forth rich, both by their own wealth, and still more by the spoils of Egypt. Their number had grown from those seventy-five Hebrews, who had first gone down into Egypt, to six hundred thousand men. Now, there had elapsed from the time when Abraham first reached the land of the Canaanites a period of four hundred and thirty years, but from the deluge a period of five hundred and seventy-five years. Well, as they went forth in haste, a pillar of cloud by day, and a pillar of fire by night, marched before them.
But since, owing to the fact that the gulf of the Red Sea lay between, the way led by the land of the Philistines, in order that an opportunity might not afterwards be offered to the Hebrews, shrinking from the desert, of returning into Egypt by a well-known road through a continuous land-journey, by the command of God they turned aside, and journeyed towards the Red Sea, where they stopped and pitched their camp. When it was announced to the king that the Hebrew people, through mistaking the road, had come to have the sea right before them, and that they had no means of escape since the deep would prevent them, vexed and furious that so many thousand men should escape from his kingdom and power, he hastily led forth his army.
And already the arms, and standards, and the lines drawn up in the widespreading plains were visible, when, as the Hebrews were in a state of terror, and gazing up to heaven, Moses being so instructed by God, struck the sea with his rod, and divided it. Thus a road was opened to the people as on firm land, the waters giving way on both sides. Nor did the king of Egypt hesitate to follow the Israelites going forward, for he entered the sea where it had opened; and, as the waters speedily came together again, he, with all his host, was destroyed.
Source: Sacred History (New Advent)