פירוש על עמוס 4:6

Cleanness of teeth Heb. נִקְיוֹן שִׁ נַּיִם. Setting your teeth on edge. [I.e, they would have nothing to eat, and their teeth would be set on edge.] Another explanation: cleanness of teeth. This denotes the lack of meat, which goes between the teeth, as it is stated: (Num. 11:33) “The meat was still between their teeth.”