C. F. Keil and Franz Delitzsch on Ecclesiastes 10:20

Ecc 10:20 “Curse not the king even in thy thought; and in thy bed-chamber curse not the rich; for the birds of the air carry away the sound, and the winged creature telleth the matter.” In the Books of Daniel and Chronicles, מדּע, in the sense of γνῶσις, is a synon. of השׂכּל and חכמה; here it is rightly translated by the lxx by συνείδησις; it does not correspond with the moral-religious idea of conscience, but yet it touches it, for it designates the quiet, inner consciousness (Psychol. p. 134) which judges according to moral criteria: even (gam, as e.g., Deu 23:3) in the inner region of his thoughtsHengst., not finding the transition from scientia to conscientia natural, gives, after Hartmann, the meaning of “study-chamber” to the word מדּע; but neither the Heb. nor the Aram. has this meaning, although Psa 68:13 Targ. touches it. one must not curse the king (cf. Ecc 7:4.) nor the rich (which here, as at 6b, without distinction of the aristocracy of wealth and of birth, signifies those who are placed in a high princely position, and have wealth, the nervus rerum, at their disposal) in his bed-chamber, the innermost room of the house, where one thinks himself free from treachery, and thus may utter whatever he thinks without concealment (2Ki 6:12): for the birds of the air may carry forth or bring out (Lat. deferrent, whence delator) that which is rumoured, and the possessor of a pair of wings (cf. Pro 1:17), after the Chethı̂b (whose ה of the art. is unnecessarily erased by the Kerı̂,הכּן with unpointed He, because it is not read in the Kerı̂; similarly החנית (1Sa 26:22). Cf. Mas. fin. f. 22, and Ochla veochla, No. 166. as at Ecc 3:6, Ecc 3:10): the possessor of wings (double-winged), shall further tell the matter. As to its meaning, it is the same as the proverb quoted by the Midrash: “walls have ears.”Vid., Tendlau’s Sprichwörter, No. 861.

Geier thinks of the swallows which helped to the discovery of Bessus, the murderer of his father, and the cranes which betrayed the murderer of Ibycus, as comparisons approaching that which is here said. There would certainly be no hyperbole if the author thought of carrier-pigeons (Paxton, Kitto) in the service of espionage. But the reason for the warning is hyperbolical, like an hundred others in all languages:“Aures fert paries, oculos nemus: ergo cavere Debet qui loquitur, ne possint verba nocere.”