Kautilya's Arthashastra 7.16.26

7.16.26

na ca hatasya bhūmidravyaputradārān abhimanyeta //

He should never covet the land, things, and sons and wives of the king slain by him; he should reinstate in their own estates the relatives of the kings slain. He should install in the kingdom the heir-apparent of the king who has died while working (with the conqueror); all conquered kings will, if thus treated, loyally follow the sons and grandsons of the conqueror.