Parashas Vayechi · Passuk 48:4
And said unto me: Behold, I will make thee fruitful, and multiply thee, and I will make of thee a company of peoples; and will give this land to thy seed after thee for an everlasting possession.
Torah Temimah points to Horayos 6b (and related discussion of “kehal”).
TT lemma: ונתתיך לקהל עמים.
English: And who was born to him at that time? Binyamin. Infer from this that the Merciful One said to him: “There will be born to you now another kehilla.” Infer from this that even a single tribe is called a kehilla.
Derash on the verse (Bavli sugya) — the fulfillment of the promise through the birth of only one additional son (Binyamin) proves that a single tribe is already termed “kehal.”
A single shevet is called a kehilla. The promise “I will make of thee a company of peoples” was realized with the birth of Binyamin, establishing the minimal size of a kehal.