וַיְהִ֗י בִּתְחִלַּת֙ שִׁבְתָּ֣ם שָׁ֔ם לֹ֥א יָרְא֖וּ אֶת־יְהוָ֑ה וַיְשַׁלַּ֨ח יְהוָ֤ה בָּהֶם֙ אֶת־הָ֣אֲרָי֔וֹת וַיִּֽהְי֥וּ הֹרְגִ֖ים בָּהֶֽם׃
And so it was, at the beginning of their dwelling there, that they feared not the LORD; therefore the LORD sent lions among them, which killed some of them.
Bartenura
על הכותית – This Tanna/teacher holds that Kutim are “lion-proselytes,” (i.e., proselytes from mere fear, with reference to II Kings 17:25) and are considered as heathens.
Rashi
They are lion-proselytes - it is explained in the book of Kings: "GOD sent lions against them" [II Kings 17:25] and that there was written regarding Samaritans: "The king of Assyria brought [people] from ... Cuthah" [II Kings 17:24]. Other locations are [also] indicated [there].