Mbh 12.95.4a

"'Bhishma said, "A Kshatriya must not put on armour for fighting a Kshatriya unclad in mail. One should fight one, and abandon the opponent when the latter becomes disabled.[280] If the enemy comes clad in mail, his opponent also should put on mail. If the enemy advances backed by an army, one should, backed by an army, challenge him to battle. If the enemy fights aided by deceit, he should be met with the aid of deceit. If, on the other hand, he fights fairly, he should be resisted with fair means. One should not on horseback proceed against a car-warrior. A car-warrior should proceed against a car-warrior. When an antagonist has fallen into distress, he should not be struck; nor should one that has been frightened, nor one that has been vanquished.[281] Neither poisoned nor barbed arrows should be used. These are the weapons of the wicked. One should fight righteously, without yielding to wrath or desiring to slay. A weak or wounded man should not be slain, or one that is sonless; or one whose weapon has been broken; or one that has fallen into distress; or one whose bow-string has been cut; or one that has lost his vehicle. A wounded opponent should either be sent to his own home, or, if brought to the victor's quarters, should have his wounds attended to by skilful surgeons. When in consequence of a quarrel between righteous kings, a righteous warrior falls into distress, (his wounds should be attended to and) when cured he should be set at liberty. This is the eternal duty. Manu himself, the son of the Self-born (Brahman), has said that battles should be fought fairly. The righteous should always act righteously towards those that are righteous. They should adhere to righteousness without destroying it. If a Kshatriya, whose duty it is to fight righteously, wins a victory by unrighteous means, he becomes sinful. Of deceitful conduct, such a person is said to slay his own self. Such is the practice of those that are wicked.