Sirach 32:7-9

New Revised Standard Version Catholic Edition

⁷ Speak, you who are young, if you are obliged to,
    but no more than twice, and only if asked.
⁸ Be brief; say much in few words;
    be as one who knows and can still hold his tongue.
⁹ Among the great do not act as their equal;
    and when another is speaking, do not babble.