This freedom from absolute, arbitrary power, is so necessary to, and closely joined with a man’s preservation, that he cannot part with it, but by what forfeits his preservation and life together: for a man, not having the power of his own life, cannot, by compact, or his own consent, enslave himself to any one, nor put himself under the absolute, arbitrary power of another, to take away his life, when he pleases. No body can give more power than he has himself ; and he that cannot take away his own life, cannot give another power over it. Indeed, having by his fault forfeited his own life, by some act that deserves death ; he, to whom he has forfeited it, may (when he has him in his power) delay to take it, and make use of him to his service, and he does him no injury by it: for, whenever he finds the hardship of his slavery outweigh the value of his life, it is in his power, by resisting the will of his master, to draw on himself the death he desires (Locke 206-207).
Locke, John. “Of Slavery.” Two Treatises of Government, 1689, pp. 205-07.