The Master said, "The superior man wishes to be slow in his speech and earnest in his conduct."
子曰、君子欲訥於言、而敏於行。
Analects 4.24
The same idea in other traditions
Keep thy tongue from evil, And thy lips from speaking guile.
A soft answer turneth away wrath: but grievous words stir up anger.
Not to commit any sin, to do good, and to purify one's mind, that is the teaching of (all) the Awakened.
Humility is the word, forgiveness is the virtue, and sweet speech is the magic mantra. Wear these three robes, O sister, and you will captivate your Husband Lord.
And pursue not that of which thou hast no knowledge; for every act of hearing, or of seeing or of (feeling in) the heart will be enquired into (on the Day of Reckoning).
Be silent, O thou who knowest many things! for he that speaketh little will be free from reproach on the Day of Judgment. The man of many words is deaf; no counsel does he heed like silence. …
By watchfulness of the mind he concentrates his thoughts; thereby he truly practises control. By watchfulness of speech he keeps free from prevarication; thereby he enables his mind to act properly.