Mbh 9.58.2a

"'Vasudeva said, "The instruction received by them hath been equal. Bhima, however, is possessed of greater might, while the son of Dhritarashtra is possessed of greater skill and hath laboured more. If he were to fight fairly, Bhimasena will never succeed in winning the victory. If, however, he fights unfairly he will be surely able to slay Duryodhana. The Asuras were vanquished by the gods with the aid of deception. We have heard this. Virochana was vanquished by Shakra with the aid of deception. The slayer of Vala deprived Vritra of his energy by an act of deception. Therefore, let Bhimasena put forth his prowess, aided by deception! At the time of the gambling, O Dhananjaya, Bhima vowed to break the thighs of Suyodhana with his mace in battle. Let this crusher of foes, therefore, accomplish that vow of his. Let him with deception, slay the Kuru king who is full of deception. If Bhima, depending upon his might alone, were to fight fairly, king Yudhishthira will have to incur great danger. I tell thee again, O son of Pandu, listen to me. It is through the fault of king Yudhishthira alone that danger hath once more overtaken us! Having achieved great feats by the slaughter of Bhishma and the other Kurus, the king had won victory and fame and had almost attained the end of the hostilities. Having thus obtained the victory, he placed himself once more in a situation of doubt and peril. This has been an act of great folly on the part of Yudhishthira, O Pandava, since he hath made the result of the battle depend upon the victory or the defeat of only one warrior! Suyodhana is accomplished, he is a hero; he is again firmly resolved. This old verse uttered by Usanas hath been heard by us. Listen to me as I recite it to thee with its true sense and meaning! 'Those amongst the remnant of a hostile force broken flying away for life, that rally and come back to the fight, should always be feared, for they are firmly resolved and have but one purpose!