Akademik

Нужно молчать, коли нечего сказать

It is better not to speak up if you cannot give a reasonable opinion. See Лучше молчать, чем пустое врать (Л)

Var.: Не стыдно молчать, коли нечего сказать

Cf: Be silent, or say something better than silence (Br.). Be silent or speak something worth hearing (Am.). Better say nothing than not to the purpose (Br.). If it isn't worth saying, don't say it at all (Am.). Say well or be still (Br.). Silence is wisdom when speaking is folly (Am., Br.). Speak fitly or be silent wisely (Am., Br.). When you have nothing to say, say nothing (Br.)

Русско-английский словарь пословиц и поговорок. Академик.ру. 2013.