And any person, whether a native or a stranger (gair), who eats carrion (nevaila) or what was torn (trief), shall immerse his garments and immerse himself in the waters, and shall remain unclean until evening, and then he shall become clean.
Why is the stranger included in this requirement to be purified after eating non-kosher meat?
EDIT: If "gair" means convert in this case, why does it even need to mention whether or not the person is a convert? Additionally, how do you know when the word means convert and when it means non-Jew? For example, Devarim 14:21 says:
You shall not eat any carcass. You may give it to the stranger (gair) who is in your cities, that he may eat it...