Mbh 12.114.2b

That man who speaks of one's merits when one's eye is upon him and who speaks ill of one when one's eye is withdrawn from him, is really like a dog. Such a person loses all his regions in heaven and the fruits of any knowledge and virtue that he may have.[350] The man who speaks ill of one when one's eye is not upon him, loses without delay the fruits of all his libations on fire and of the gifts he may make unto even a hundred persons. A man of wisdom, therefore, should unhesitatingly avoid a person of such sinful heart who deserves to be avoided by all honest men, as he would avoid the flesh of the dog. That wicked-souled wretch who proclaims the faults of a high-souled person, really publishes (by that act) his own evil nature even as a snake displays his hood (when interfered with by others). The man of sense who seeks to counteract such a back-biter ever engaged in an occupation congenial to himself, finds himself in the painful condition of a stupid ass sunk in a heap of ashes. A man who is ever engaged in speaking ill of others should be avoided like a furious wolf, or an infuriated elephant roaring in madness, or a fierce dog. Fie on that sinful wretch who has betaken himself to the path of the foolish and has fallen away from all wholesome restraints and modesty, who is always engaged in doing what is injurious to others, and who is regardless of his own prosperity. If an honest man wishes to exchange words with such wretches when they seek to humiliate him, he should be counselled in these words: Do not suffer thyself to be afflicted. A wordy encounter between a high and a low person is always disapproved by persons of tranquil intelligence. A slanderous wretch, when enraged, may strike another with his palms, or throw dust or chaff at another, or frighten another by showing or grinding his teeth. All this is well known.