Before setting out, Confucius tells his disciple
南宫敬叔 that
老聃 (Laozi) knows antiquity and understands the present and is fit to be his teacher, the praise behind the idiom
博古通今. In the Zhou ancestral temple he then sees a bronze statue whose mouth is sealed three times, a warning against careless speech, which is where
三缄其口 'to keep one's lips sealed' comes from.
