Matsya Purana 261.14

261.14

mahāmahiṣamārūḍhaṃ kṛṣṇāñjanacayopamam.
siṃhāsanagatañcāpi dīptāgnisamalocanam .. 261.13

Or he is to have seven heads with seven burning rays and He is to be placed in the kuṇḍa sacrificial pit) The image of Dharmarâja should be made holding a mace and a noose, riding a huge buffalo black like soot and seated on a throne, with eyes sparkling like fire Round His image should be made the images of Chitragupta some formidable attendants, groups of quiet and formidable Demons and the great buffalo—12 14