Parashas Bamidbar
אַל־תַּכְרִ֕יתוּ אֶת־שֵׁ֖בֶט מִשְׁפְּחֹ֣ת הַקְּהָתִ֑י מִתּ֖וֹךְ הַלְוִיִּֽם׃
Do not let the group of Kohathite clans be cut off from the Levites.
Torah Temimah points to TT / related (verified).
אל תכריתו — תניא, המת לחמשים שנה זו מיתת כרת.
English: “Do not cut off” — it was taught: One who dies at fifty years — this is the death of kares.
Custom
Chazal associate the language of “cutting off” with the classification of death at fifty as kares.