From: Oromo, East Africa
Source: Oromo (Ethiopia) proverb; original text, translation and explanation from Megersa Regassa Tolasa and Dejene Gemechu Chala, "Oromo Proverbs and Proverbial Expressions in the Customary Judicial System in Ethiopia," Journal of Ethnology and Folkloristics 13(2), 2019.
The source explains it: used to indicate the importance of polite communication and to criticise attitudes of disrespect; the insult that comes from the tongue can harm others psychologically
. The wording of the meaning is ours.