Mbh 4.26.2a

Vaisampayana said, “Having listened to these words of his spies, king Duryodhana reflected inwardly for some time and then addressed his courtiers, saying, ‘It is difficult to ascertain the course of events definitely. Discern ye all, therefore, whither the sons of Pandu have gone, of this thirteenth year which they are to pass undiscovered by us all, the greater part hath already expired. What remains is by much the smaller. If, indeed, the sons of Pandu can pass undiscovered what remains of this year, devoted to the vow of truth as they are, they will then have fulfilled their pledge. They will then return like mighty elephants with temporal juice trickling down, or like snakes of virulent poison. Filled with wrath, they will, without doubt, be inflicters of terrible chastisement on the Kurus. It behoveth ye, therefore, to make such efforts without loss of time as may induce the sons of Pandu, acquainted as they are with the proprieties of time, and staying as they now are in painful disguise, to re-enter the woods suppressing their rage. Indeed, adopt ye such means as may remove all causes of quarrel and anxiety from the kingdom, making it tranquil and foeless and incapable of sustaining a diminution of territory.’ Hearing these words of Duryodhana, Karna said, ‘Let other spies, abler and more cunning, and capable of accomplishing their object, quickly go hence, O Bharata. Let them, well-disguised, wander through swelling kingdoms and populous provinces, prying into assemblies of the learned and delightful retreats of provinces. In the inner apartments of palaces, in shrines and holy spots, in mines and diverse other regions, the sons of Pandu should be searched after with well-directed eagerness. Let the sons of Pandu who are living in disguise be searched after by well-skilled spies in large numbers, devoted to their work, themselves well-disguised, and all well-acquainted with the objects of their search.