Numbers 15:14 - Joseph Benson’s Commentary on the Old and New Testaments

If a stranger sojourn with you It is plain this is to be understood of such strangers as had renounced idolatry and become proselytes to the worship of the true God. And if strangers, who were intermixed with the Jews, and resided in their country, had not been obliged to conform to the same ceremonies of public worship with the Jews, their example might, by degrees, have produced a change in, and corruption of, that form of worship which God himself had instituted.