xìn yán bù měi, měi yán bù xìn 信言不美，美言不信
Trustworthy Words May Not Be Fine-sounding; Fine-sounding Words May Not Be Trustworthy.
To address the extravagance in social mores and in the style of writing of his time, Laozi advocated simple and natural lifestyles and literary presentations. During the Wei and Jin dynasties, men of letters valued natural and simple literary styles and were opposed to extravagant and superficial styles. This line of thought led to the emergence of great poets like Tao Yuanming, and shaped literary writings to reflect direct thoughts and natural expressions. Subsequently, ancient Chinese literature and art took simplicity and naturalness as the highest aesthetic standards.
Trustworthy words may not be fine-sounding; fine-sounding words may not be trustworthy. A kind-hearted person may not be an eloquent speaker; a glib person is often not kind. (Laozi)
Laozi detested pretense, so he said, “Flowery rhetoric words may not be trustworthy.” However, the 5,000-word Dao De Jing (another name of Laozi) he wrote is not only profound in ideas but reads beautifully. That means he was not opposed to writings using fine words. (Liu Xie: The Literary Mind and the Carving of Dragons)