Mbh 12.69.2a

"'Bhishma said, "Listen, O monarch, with attention to the diverse duties of kings,--to those acts which the king or one that is in the position of a king should first do. The king should first subdue himself and then seek to subdue his foes. How should a king who has not been able to conquer his own self be able to conquer his foes? The conquest of these, viz., the aggregate of five, is regarded as the conquest of self. The king that has succeeded in subduing his senses is competent to resist his foes. He should place bodies of foot-soldiers in his forts, frontiers, towns, parks, and pleasure gardens, O delighter of the Kurus, as also in all places where he himself goes, and within his own palace, O tiger among men! He should employ as spies men looking like idiots or like those that are blind and deaf. Those should all be persons who have been thoroughly examined (in respect of their ability), who are possessed of wisdom, and who are able to endure hunger and thirst. With proper attention, the king should set his spies upon all his counsellors and friends and sons, in his city and the provinces, and in dominions of the chiefs under him. His spies should be so employed that they may not know one another. He should also, O bull of Bharata's race, know the spies of his foes by himself setting spies in shops and places of amusement, and concourses of people, among beggars, in his pleasure gardens and parks, in meetings and conclaves of the learned, in the country, in public places, in places where he holds his own court, and in the houses of the citizens. The king possessed of intelligence may thus ascertain the spies despatched by his foes. If these be known, the king may derive much benefit, O son of Pandu! When the king, by a survey of his own, finds himself weak, he should then, consulting with his counsellors make peace with a foe that is stronger.