John Gill 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)

Seven days there shall be no leaven found in your houses , &c.]. Wherefore, on the fourteenth day the most diligent search was made, and whatever was found was burnt, or cast into the sea, or dispersed with the wind; about which the traditionary writers of the Jews, give many rules and canons, (See Gill on Exodus 12:15),

for whoso eateth that which is leavened, even that soul shall be cut off from the congregation of Israel ; which is repeated to deter them from the breach of this ordinance; (See Gill on Exodus 12:15), and it is added for further explanation, of whom it concerns: whether he be a stranger, or born in the land ;

by a "stranger" is meant, not a mere Heathen, who was not bound by this law, but a proselyte; and not a proselyte of the gate, one that was only a sojourner among them, and observed the commandments of the sons of Noah; but a proselyte of righteousness, who professed the Jewish religion, and proposed to conform to it in all respects, and therefore was obliged to observe this as other precepts:

and by one "born in the land", is intended a native of the land of Canaan, whither they were now going in order to possess it, or a real Israelite, such as were born of Israelitish parents, and proper inhabitants of Canaan, which they would be put into the possession of.