an eye for an eye 指对所受冒犯以牙还牙。人们有时用这一谚语替个人甚至国家在冲突中的报复行为进行辩解。
它源自《钦定版圣经》中《出埃及记》（Exodus）第21章第22－24节：
If men strive, and hurt a woman with child, so that her fruit depart from her, and yet no mischief follow: he shall be surely punished, according as the woman's husband will lay upon him; and he shall pay as the judges determine. And if any mischief follow, then thou shalt give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burning for burning, wound for wound, stripe for stripe.
人若彼此争斗，伤害有孕的妇人，以至其坠胎，随后却无别害，那伤害她的，总要按妇人的丈夫所要的，照审判官所断的，受罚。若有别害，就要以命偿命，以眼还眼，以牙还牙，以手还手，以脚还脚，以烙还烙，以伤还伤，以打还打。
