NOTES for Exo 12:29-51
The death of the firstborn was the last straw: Pharaoh lets the people go. More than that, he hurries the Hebrews to leave. Why? Did Pharaoh think the Hebrews would want to leave Egypt? Later events will show clearly: no, he did not. The expectation was that the people would go to Beersheba, where there was an old Yahwist sanctuary that had existed since the time of Abraham, to Beersheba, which was then under Egyptian control. From the delta region it was about a three-day journey one way.
Pharaoh hoped that the Hebrews would go to Beersheba, offer the required sacrifices to their God, celebrate their feast, and return. Pharaoh now understood: otherwise he would not be rid of the wrath of Moses' God. Ordinary Egyptians thought the same. The story mentions that the Hebrews "plundered" the Egyptians. They certainly could not have done any such thing by force. Something else was quite possible: the Egyptians brought them offerings for their God.
That was an old Egyptian custom, and not only Egyptian: in order to be healed from illness or to avoid death, one had to bring an offering to the god who was probably or clearly the cause of the misfortune. As a rule, it was an amulet that directly or symbolically depicted what one wanted to get rid of. Amulets were made of gold, silver, or copper; and if a person could not afford anything of the sort, then of clay. Something else could also be donated if the cause of the misfortune was not exactly known: why, for example, the firstborn had died was rather hard for the Egyptians to determine. Often people donated the same gold or silver items so that the god's wrath would not touch the donor.
The Egyptians, as we see, had already become convinced: whoever Moses' God was, He was not to be trifled with. Simple people, untrained in theological subtleties, might consider Him some stern spirit of the desert, one of those whom, according to their ideas, nomads worshiped. In any case, this unknown god or spirit had to be appeased, for death had entered every house, and no one knew what to expect next. Both the authorities and ordinary people now looked at Moses as a savior, the only one who could save the country from otherwise inevitable destruction.