Mbh 3.149.4c

Then only is the order of the world secured, when the king duly punisheth and conferreth favours. Therefore, it is necessary to ascertain through spies the nature of the hostile country, its fortified places and the allied force of the enemy and their prosperity and decay and the way in which they retain the adhesion of the powers they have drawn to their side. Spies are among the important auxiliaries of the king; and tact, diplomacy, prowess, chastisement, favour and cleverness lead to success. And success is to be attained through these, either in separation, or combined--namely, conciliation, gift, sowing dissensions, chastisement, and sight. And, O chief of the Bharatas, polity hath for its root diplomacy; and diplomacy also is the main qualification of spies. And polity, if well judged conferreth success. Therefore, in matters of polity the counsels of Brahmanas should be resorted to. And in secret affairs, these should not be consulted,--namely, a woman, a sot, a boy, a covetous person a mean-minded individual, and he that betrayeth signs of insanity. Wise men only should be consulted, and affairs are to be despatched through officers that are able. And polity must be executed through persons that are friendly; but dunces should in all affairs be excluded. In matters religious, pious men; and in matters of gain, wise men; and in guarding families, eunuchs; and in all crooked affairs, crooked men, must be employed. And the propriety or impropriety of the resolution of the enemy, as also their strength or weakness, must be ascertained through one’s own as well as hostile spies. Favour should be shown to honest persons that have prudently sought protection; but lawless and disobedient individuals should be punished. And when the king justly punisheth and showeth favour, the dignity of the law is well maintained, O son of Pritha, thus have I expounded, unto thee the hard duties of kings difficult to comprehend.