Horayot 6B

אלא מעתה נייתו פר בהוראה! וכי תימא, הכי נמי ⁠– טפי להו שבטים.

The Talmud challenges: If that is so, that the priests are characterized as a congregation, let them bring a bull as an unwitting communal offering if they perform a transgression on the basis of the ruling of the court. And if you would say indeed it is so, that is difficult, as the number of tribes has increased to 13.

אלא אמר רב אחא ברבי יעקב: שבטו של לוי לא איקרו קהל, דכתיב: ״הנני מפרך והרביתך ונתתיך לקהל עמים וגו׳״. כל שיש לו אחוזה ⁠– איקרי קהל, וכל שאין לו אחוזה ⁠– לא איקרי קהל.

Rather, Rav Aḥa, son of R' Ya’akov, said: The tribe of Levi is not characterized as a congregation, as it is written: “Behold, I will make you fruitful and multiply you, and I will make of you a congregation of peoples; and I will give this land to your descendants after you for an everlasting possession” (Genesis 48:4). It is derived from here that any tribe that has an ancestral possession bequeathed to it is characterized as a congregation, and any tribe that does not have an ancestral possession bequeathed to it is not characterized as a congregation. The tribe of Levi has no ancestral land, and the priests who are from the tribe of Levi have no ancestral land.

אם כן, חסרי להו שנים עשר שבטים! אמר אביי: ״אפרים ומנשה כראובן ושמעון יהיו לי״. אמר רבא, והא כתיב: ״על שם אחיהם יקראו בנחלתם״, לנחלה הוקשו ולא לדבר אחר!

The Talmud challenges: If so, the 12 tribes are lacking in number, as without the tribe of Levi there are only 11. Abaye said that it is stated: “Ephraim and Manasseh should be like Reuben and Shimon to me” (Genesis 48:5), and they are counted as two tribes. Rava said: But isn’t it written: “After the name of their brothers should they be called in their inheritance” (Genesis 48:6), indicating that it is with regard to inheritance that they are likened to tribes, but not with regard to another matter?