口者關也，舌者兵也，出言不當，反自傷也。
When you speak amiss, not even a team of horses can overtake your words.
言出於己，不可止於人；行發於邇，不可止於遠。
The mouth is a mountain pass and the tongue a weapon. If you speak amiss, your words will turn back and injure you.
夫言行者，君子之樞機。
Words issue forth from the self but are unable to stop upon reaching others; actions proceed from what is right at hand but are not able to stop before going far.
Speech and action, let us note, are regarded by a man of quality as crucial hinges of affairs.
樞機之發，榮辱之本也，可不慎乎！
Once these hinges are set in motion, they become the sources both of glory and disgrace.
故蒯子羽曰：「言猶射也：栝既離弦，雖有所悔焉，不可從而退已。
How can one not be wary of them!
」詩曰：「白珪之玷，尚可磨也；斯言之玷，不可為也。」
Thus, Kuaizi Yu20 said, “Saying something is like shooting an arrow; once the feathers depart from the string, there is no way, though one may feel regret, that one can overtake the arrow.” As is said in the Odes, “A flaw in a piece of jade / Can still be ground away; / But, for a flaw in speech, / Nothing can be done at all.”22 20 Kuaizi Yu 蒯子羽: unattested elsewhere.
“Feathers”: the tail end of an arrow.