one should not speak ill of powerful figures, even in private

 Ecclesiastes 10:20 conveys the message that one should not speak ill of powerful figures, even in private, as they might find out. The verse reads: 

 English Standard Version

"Even in your thoughts, do not curse the king, nor in your bedroom curse the rich, for a bird of the air will carry your voice, or some winged creature tell the matter" 

 The Message

"Don't bad-mouth your leaders, not even under your breath, And don't abuse your betters, even in the privacy of your home" 

 The verse is part of Ecclesiastes, which emphasizes the unpredictable nature of life. It encourages people to be prudent when criticizing authority, especially when change seems unattainable. The verse also serves as a reminder that secrets will eventually be revealed.