Negative commandment · Lo Ta’aseh #133 of 613
For an unauthorized person not to partake of the terumot
שלא יאכל זר תרומות
The verse · Vayikra 22:10
וְכׇל־זָר לֹא־יֹאכַל קֹדֶשׁ תּוֹשַׁב כֹּהֵן וְשָׂכִיר לֹא־יֹאכַל קֹדֶשׁ
“No stranger shall eat of the holy thing: a tenant of a priest, or a hired servant, shall not eat of the holy thing.”
The Rambam’s words
For an unauthorized person not to partake of the terumot, as [Leviticus 22:10] states: "No unauthorized person shall eat it."
שלא יאכל זר תרומות, שנאמר "וכל זר, לא יאכל קודש" (ויקרא כב,י).
Why · Sefer HaChinuch #280
That no foreigner eat priestly tithe
“From the roots of the commandment [is] like [that which is written about] the preceding commandment.”
Who & when
“And the prohibition of the eating of priestly tithes for non-priests is practiced by all of Israel, males and females, in any place that there is priestly tithe from Torah writ — that is at the time that the Land of Israel is in its settlement, for then the obligation of priestly tithe is from Torah writ, as we will write in the Order of Shoftim (Sefer HaChinukh 507) in the commandment of separating the great priestly tithe, with G-d’s help.”
Where in the Mishneh Torah
Hilchot Heave Offerings הלכות תרומות