Jamieson, Fausset and Brown on Ecclesiastes 10:20

20. thought--literally, "consciousness."

rich--the great. The language, as applied to earthly princes knowing the "thought," is figurative. But it literally holds good of the King of kings (Psa 139:1-24), whose consciousness of every evil thought we should ever realize.

bed-chamber--the most secret place (2Ki 6:12).

bird of the air, &c.--proverbial (compare Ha 2:11; Lu 19:40); in a way as marvellous and rapid, as if birds or some winged messenger carried to the king information of the curse so uttered. In the East superhuman sagacity was attributed to birds (see on Job 28:21; hence the proverb).