Charles Ellicott Commentary Exodus 12:19

"Seven days shall there be no leaven found in your houses: for whosoever eateth that which is leavened, that soul shall be cut off from the congregation of Israel, whether he be a sojourner, or one that is born in the land." — Exodus 12:19 (ASV)

A stranger — that is, a foreigner by birth, who has been adopted into the nation, received circumcision, and become a full proselyte. It is not improbable that many of the “six hundred thousand” counted as part of “Israel” (Exodus 12:37) were of this class—persons who had joined themselves to the nation during the sojourn in Egypt, or even earlier. (See Note on Genesis 17:13.)

When the “exclusiveness” of the Hebrews is made a charge against them, justice requires us to remember that from the beginning it was open to those who were not of Hebrew blood to share in the Hebrew privileges by accepting the covenant of circumcision and joining themselves to the nation. It was in this way that the Kenites and even the Gibeonites became counted as part of Israel.

Born in the land. — Hebrew, natives of the land: that is, of Canaan. Canaan was regarded as belonging to Abraham and his descendants from the time of the first promise (Genesis 12:7). From that time forward, it was their true home: they were its expatriated inhabitants.