John Gill Commentary Numbers 15:16

"One law and one ordinance shall be for you, and for the stranger that sojourneth with you." — Numbers 15:16 (ASV)

One law, and one manner
One law respecting these sacrifices, and one manner of offering them; one and the same precept to be observed, and one and the same judgment or punishment inflicted in case of non-observance:

shall be for you, and the stranger that sojourns with you ;
for Israelites and proselytes; which is said to invite and encourage the latter, and may have a distant view to the calling of the Gentiles in Gospel times, when there should be no difference between Jews and Gentiles called by grace in matters of religion, but would be one in Christ, (Galatians 3:28) .