Who said "In matters of conscience, a man must act alone."?

This quote is attributed to O. Henry.

In matters of conscience, a man must act alone. - O. Henry

"In matters of conscience, a man must act alone."

O. Henry Courage

Writer American 1862–1910

"Turn up the lights. I don't know what time it is."

"We are not made by our circumstances, we are made by our choices."

"Life is made up of sobs, sniffles, and smiles, with sniffles predominating."

"A stitch in time may have ten times the sequel."

"Never let fear stop you from chasing your dreams."

"Courage is being afraid but doing it anyway."

"Sometimes you gotta do what you gotta do."

"Sometimes you have to be the monster to stop the monsters."