Eating without sharing is like swearing with your mouth.

What it means
Eating in front of people who have nothing, without sharing, is an insult as real as cursing at them. Generosity is expected, and holding it back is an offense, not a neutral choice.
Tswana · Southern Africa
Source and context
From: Tswana, Southern Africa
Source: Botswana oral-tradition proverbs — "Some Botswana Proverbs," African Studies Center, Boston University

The meaning given here is our own reading. Other interpretations exist.