Mbh 12.138.2

"'Bhishma said, "O Yudhishthira, this question is certainly worthy of thee. Its answer is fraught with great happiness. Listen to me, O son, as I declare to thee, O Bharata, all the duties generally known that should be practised in seasons of distress. A foe becomes a friend and a friend also becomes a foe. The course of human actions, through the combination of circumstances, becomes very uncertain. As regards, therefore, what should be done and what should not, it is necessary that paying heed to the requirements of time and place, one should either trust one's foes or make war. One should, even exerting one's self to one's best, make friends with men of intelligence and knowledge that desire one's welfare. One should make peace with even one's foes, when, O Bharata, one's life cannot otherwise be saved. That foolish man who never makes peace with foes, never succeeds in winning any gain or acquiring any of those fruits for which others endeavour. He again who makes peace with foes and quarrels with even friends after a full consideration of circumstances, succeeds in obtaining great fruits. In this connection is cited the old story of the discourse between a cat and a mouse at the foot of a banian."