Mbh 12.96.1a

"'Bhishma said, "A king should never desire to subjugate the earth by unrighteous means, even if such subjugation would make him the sovereign of the whole earth. What king is there that would rejoice after obtaining victory by unfair means? A victory stained by unrighteousness is uncertain and never leads to heaven. Such a victory, O bull of Bharata's race, weakens both the king and the earth. A warrior whose armour has fallen off, or who begs for quarter, saying, 'I am thine' or joining his hands, or who has laid aside his weapon, may simply be seized but never slain. If a hostile king be vanquished by the troops of the invader, the latter should not himself fight his vanquished foe. On the other hand, he should bring him to his palace and persuade him for a whole year to say, 'I am thy slave!' Whether he says or does not say this, the vanquished foe, by living for a year in the house of his victor, gains a new lease of life.[282] If a king succeeds in bringing by force a maiden from the house of his vanquished foe, he should keep her for a year and ask her whether she would wed him or any one else. If she does not agree, she should then be sent back. He should behave similarly in respect of all other kinds of wealth (such as slaves) that are acquired by force. The king should never appropriate the wealth confiscated from thieves and others awaiting execution. The kine taken from the enemy by force should be given away to the Brahmanas so that they may drink the milk of those animals. The bulls taken from the enemy should be set to agriculture work or returned to the enemy.[283] It is laid down that a king should fight one that is a king. One that is not a king should never strike one that is a king. If a Brahmana, desirous of peace, fearlessly goes between two contending armies, both should immediately abstain from fight. He would break an eternal rule that would slay or wound a Brahmana. If any Kshatriya breaks that rule, he would become a wretch of his order.