Mahabharata 3.70.26

3.70.26

yatheṣṭaṃ tvaṃ gṛhāṇedamakṣāṇāṃ hṛdayaṃ param |
nikṣepo me'śvahṛdayaṃ tvayi tiṣṭhatu bāhuka |
evamuktvā dadau vidyāmṛtuparṇo nalāya vai || 26 ||

Then the king reluctantly told him, 'Count. And on counting the leaves and fruits of a portion of this branch, thou wilt be satisfied of the truth of my assertion.' And thereupon Vahuka speedily alighted from the car, and felled that tree. And struck with amazement upon finding the fruits, after calculation, to be what the king had said, he addressed the king, saying, 'O monarch, this thy power is wonderful. I desire, O prince, to know the art by which thou hast ascertained all this.' And at this king, intent upon proceeding speedily, said unto Vahuka. 'Know that I am proficient at dice besides being versed in numbers. And Vahuka said unto him, 'Impart unto me this knowledge and, O bull among men, take from me my knowledge of horses.' And king Rituparna, having regard to the importance of the act that depended upon Vahuka's good-will, and tempted also by the horse-lore (that his charioteer possessed), said, 'So be it.' As solicited by thee, receive this science of dice from me, and, O Vahuka, let my equine science remain with thee in trust.' And saying this, Rituparna imparted unto Nala the science (he desired). And Nala upon becoming acquainted with the science of dice, Kali came out of his body, incessantly vomiting from his mouth the virulent poison of Karkotaka.