“You gain power by pretending to be weak.”

Source: De Moneta (c. 1360), Ch. 15: That the Profit accruing to the Prince from Alteration of the Coinage is unjust

I Corinthians 9:22 (KJV)
First Epistle to the Corinthians
Context: Though I be free from all men, yet have I made myself servant unto all, that I might gain the more. And unto the Jews I became as a Jew, that I might gain the Jews; to them that are under the law, as under the law, that I might gain them that are under the law; To them that are without law, as without law, (being not without law to God, but under the law to Christ,) that I might gain them that are without law. To the weak became I as weak, that I might gain the weak: I am made all things to all men, that I might by all means save some.

Act V, scene i.
Aminta (1573)

Section 42
The Passionate State Of Mind, and Other Aphorisms (1955)
Context: It has often been said that power corrupts. But it is perhaps equally important to realize that weakness, too, corrupts. Power corrupts the few, while weakness corrupts the many. Hatred, malice, rudeness, intolerance, and suspicion are the faults of weakness. The resentment of the weak does not spring from any injustice done to them but from the sense of inadequacy and impotence. They hate not wickedness but weakness. When it is their power to do so, the weak destroy weakness wherever they see it.

Verse XXV.10
Tirukkural

Book 2, Chapter 2 “In Which Old Acquaintances Are Resumed and New Agreements Reached” (p. 226)
The Elric Cycle, The Revenge of the Rose (1991)