an eye for an eye A law which sanctions revenge; to repay in kind. This line from Exodus 21:24 is part of a longer passage in which the Lord sets forth the judgments and laws according to which the people are instructed to live. However, this expression may be even older if, as some speculate, it was part of the Code of Hammurabi (approx. 1800 B.c.). The noted resemblances between Hammurabi’s laws and ancient Mosaic laws make this theory plausible.

fight fire with fire To argue or fight with an opponent using his tactics or ground rules; to counter an attack with one of equal intensity. This expression refers to the method used to fight a rapidly spreading forest or grass fire. To control such a fire, a firebreak (an area cleared of trees, grass, and other flammable material) is often created some distance in front of the advancing flames. A backfire may then be set to burn the area between the major fire and the firebreak, thereby containing the fire within a limited area where it can be doused with water or dirt. Thus, fire is literally fought with fire in order to defeat it. In its figurative sense, to fight fire with fire is to contend with someone on his level, using his tactics to defeat him. The expression usually implies a lowering or abandonment of one’s principles.

fix [someone’s] wagon To get even with, avenge; to prevent, interfere with, or destroy another’s success, reputation, or expectations; to injure or kill. This expression may stem from the days of the covered wagons when a person’s entire family, possessions, and livelihood could be contained in one of these vehicles. An unscrupulous and vindictive enemy might “fix” the wagon in such a way as to assure that it would break down, causing injury to and possible destruction of both the wagon and its contents. The related expression fix [someone’s] little red wagon is an updated version, and all the more insidious in its implication of harming a child.

give [someone] a taste of [his] own medicine To pay someone back in his own coin, to requite a wrong in kind; also to give [someone] a dose of [his] own medicine. Use of the expression dates from the late 19th century.

heap coals of fire on [someone’s] head

To repay hostility with kindness; to answer bad treatment with good, supposedly in order to make one’s enemy repent. The allusion is Biblical:

The usual explanation is that the “coals of fire” supposedly melted a person’s “iciness.”

pound of flesh Vengeance; requital. This expression derives from Shakespeare’s Merchant of Venice, in which Shylock agrees to lend money to Antonio only on condition that, if the sum is not repaid on time, he be allowed a pound of Antonio’s flesh in forfeit.

The expression implies that, while the demanded retribution is justified, the yielding of it would incapacitate or destroy the giver, just as the yielding of a pound of one’s own flesh would certainly have deleterious consequences.

a Roland for an Oliver An eye for an eye, a blow for a blow; retaliation in kind. Roland and Oliver, two of Charlemagne’s paladins, had adventures which were so extraordinarily similar that it was all but impossible to determine which was the more chivalrous. Eventually, the two men met face to face in combat on an island in the Rhine, where, for five days they fought fiercely, with neither gaining an advantage. The bout climaxed when both men met simultaneous untimely deaths.

serve the same sauce To retaliate in like fashion; to fight fire with fire; to repay in kind.

Variations are serve a sop or taste of the same sauce.

tit for tat Blow for blow, an eye for an eye and a tooth for a tooth, reciprocal retaliation.

According to the OED this expression is probably a variation of the earlier tip ‘light blow’ for tap ‘light blow.’

Other conjectures claim that tit for tat came from the French tant pour tant ‘so much for so much’ or the Dutch dit vor dat ‘this for that.’ Use of the phrase dates from at least 1556.