Source, in full
On Robert Falcon Scott's ill-fated Antarctic expedition, while suffering from frostbite and sheltering from a blizzard, Oates felt he was decreasing his companions' chances of survival. Oates voluntarily left the tent; it was his 32nd birthday. He was never seen again.
Notes from Wikiquote
Quoted in R. F. Scott's diary, published as Scott's Last Expedition, ch.20