“Flattery corrupts both the receiver and the giver.”

No. 101 (26 June 1711), this has sometimes been quoted as "It is the privilege of posterity to set matters right between those antagonists who, by their rivalry for greatness, divided a whole age".
The Spectator (1711–1714)
Context: If men of eminence are exposed to censure on one hand, they are as much liable to flattery on the other. If they receive reproaches which are not due to them, they likewise receive praises which they do not deserve. In a word, the man in a high post is never regarded with an indifferent eye, but always considered as a friend or an enemy. For this reason persons in great stations have seldom their true characters drawn till several years after their deaths. Their personal friendships and enmities must cease, and the parties they were engaged in be at an end, before their faults or their virtues can have justice done them. When writers have the least opportunity of knowing the truth, they are in the best disposition to tell it.
It is therefore the privilege of posterity to adjust the characters of illustrious persons, and to set matters right between those antagonists who by their rivalry for greatness divided a whole age into factions.

XVI. Concerning sacrifices and other worships, that we benefit man by them, but not the Gods.
On the Gods and the Cosmos

Source: Debt: The First 5,000 Years (2011), Chapter Twelve, "1971–The Beginning…", p. 391

Source: Guide for the Perplexed (c. 1190), Part III, Ch.8

Section 13; often the final portion of this is quoted alone as: "Absolute faith corrupts as absolutely as absolute power."
Reflections on the Human Condition (1973)
Context: The Savior who wants to turn men into angels is as much a hater of human nature as the totalitarian despot who wants to turn them into puppets.
There are similarities between absolute power and absolute faith: a demand for absolute obedience; a readiness to attempt the impossible; a bias for simple solutions — to cut the knot rather than unravel it; the viewing of compromise as surrender; the tendency to manipulate people and "experiment with blood."
Both absolute power and absolute faith are instruments of dehumanization. Hence absolute faith corrupts as absolutely as absolute power.

Attributed