quote from Snopes:
https://www.snopes.com/fact-check/lincoln-character-power/ accessed 10/12/2021
Did Lincoln Say, ‘If You Want to Test a Man’s Character, Give Him Power’?
For nearly a century, people have made the mistake of claiming that a quotation about Lincoln was actually a quotation by him.
By Dan MacGuill, Published 25 September 2019
... The full quotation is usually given as, “Nearly all men can stand adversity, but if you want to test a man’s character, give him power.”
In reality, Lincoln never uttered or wrote those words, or words to that effect. Rather, they were said about him. The original version of the quotation came on Jan. 16, 1883, during a speech in Washington, D.C., by the prominent writer and orator Robert Ingersoll.
According to newspaper reports, Ingersoll was introducing another speaker, who was scheduled to give a lecture on Lincoln, at an unspecified “auditorium” in the nation’s capital. During the course of his introductory remarks (which were printed in full by the press), Ingersoll said:
“… If you want to know the difference between an orator and a speaker, read the oration of Lincoln at Gettysburg, and then read the speech of Everett at the same place. One came from the heart, the other was born only of the voice. Lincoln’s speech will be remembered forever. Everett’s no man will read. It was like plucked flowers. [Applause].
“If you want to find out what a man is to the bottom, give him power. Any man can stand adversity — only a great man can stand prosperity. It is the glory of Abraham Lincoln that he never abused power only on the side of mercy. [Applause]. He was a perfectly honest man. When he had power, he used it in mercy …”
A modified version of those lines later appeared in published volumes of Ingersoll’s speeches and essays. For example, in his 1895 “Abraham Lincoln, a Lecture,” he wrote:
“Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy.”
The exact same formulation of words appeared in Volume 3 of the 12-volume “Works of Robert G. Ingersoll,” which was published in 1902, three years after the well-known orator’s death. ...
