John Gill Commentary Exodus 12:43

"And Jehovah said unto Moses and Aaron, This is the ordinance of the passover: there shall no foreigner eat thereof;" — Exodus 12:43 (ASV)

And the Lord said to Moses and Aaron At the same time he acquainted them with the above things: this is the ordinance of the passover ; as before delivered, and these the laws and rules, according to which it is to be observed, as now related, both with respect to the lamb, and to the unleavened bread; and the following is an account of the persons that were to partake of it: there shall no stranger eat of it , one that is of another country, an entire Heathen, and unacquainted with, and does not profess the Jewish religion, which was the religion of God.