«فَرُبَّ أُكْلَةٍ هَاضَتِ الْآكِلَ وَحَرَمَتْهُ مَا أَكَلَ»
A single meal may harm the diner and deprive him of its benefit.
Rubba is not mechanically equivalent to “many” in every context; here it introduces a cautionary case. The verb hāḍat conveys damage or weakening. Translating it as “was digested” would reverse the warning.
The speaker uses a maxim-like line to justify his refusal to burden his hosts—or to risk bodily discomfort. “Even a single meal may harm” retains the aphoristic compression and the slight exaggeration without asserting that all meals are harmful.
Translation exercise
Compare “harmed” with “was digested” and explain why one reverses the warning.