Charles Ellicott Commentary Ecclesiastes 10:20

"Revile not the king, no, not in thy thought; and revile not the rich in thy bedchamber: for a bird of the heavens shall carry the voice, and that which hath wings shall tell the matter." — Ecclesiastes 10:20 (ASV)

Thought. —A word of later Hebrew, found only in Daniel and Chronicles.

That which has wings. —Literally, master of wings; and so also Proverbs 1:17. (Compare “master of the tongue,”Ecclesiastes 10:11.)