Mbh 12.78.4

"'Bhishma said, "Wines, salt, sesamum seeds, animals having manes, bulls, honey, meat, and cooked food, O Yudhishthira, under all circumstances, a Brahmana should avoid. A Brahmana, by selling these, would sink into hell. A Brahmana, by selling a goat, incurs the sin of selling the god of fire; by selling a sheep, the sin of selling the god of water; by selling a horse, the sin of selling the god of the sun; by selling cooked food, the sin of selling land; and by selling a cow, the sin of selling sacrifice and the Soma juice. These, therefore, should not be sold (by a Brahmana). They that are good do not applaud the purchase of uncooked food by giving cooked food in exchange. Uncooked food, however, may be given for procuring cooked food, O Bharata![234] 'We will eat this cooked food of thine. Thou mayst cook these raw things (that we give in exchange).'--In a compact of this kind there is no sin. Listen, O Yudhishthira, I shall speak to thee of the eternal practice, existing from days of old, of persons conducting themselves according to approved usages. 'I give thee this. Give me this other thing in return.' Exchange by such agreement is righteous. To take things by force, however, is sinful. Even such is the course of the usage followed by the Rishis and others. Without doubt, this is righteous."