Mishnah Berurah 199:2משנה ברורה קצ״ט:ב׳
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Shulchan Arukh, Orach Chayim 199:3שולחן ערוך, אורח חיים קצ״ט:ג׳
Someone who is an absolute am ha’aretz is included in a zimun nowadays
Berakhot 47b:4ברכות מ״ז ב:ד׳
The mishna states that a Samaritan [Kuti] may be included in a zimmun. The Gemara asks: Why? Even if you consider him a member of the Jewish people, let him be merely an am ha’aretz, one who is not scrupulous in matters of ritual purity and tithes, and it was taught in a baraita: An am ha’aretz may not be included in a zimmun.
Biur Halacha 199:3:1ביאור הלכה קצ״ט:ג׳:א׳
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