From 《
晏子春秋·
内篇杂下》. When the Qi minister
晏婴 (Yanzi) was on a mission to Chu, the king of Chu mocked the people of Qi as ill-behaved. Yanzi rebutted with 'an orange grown south of the Huai is sweet, but grown north it turns into the bitter zhi,' implying that the environment of Chu, not Qi, was what corrupted people.