Mbh 13.81.3c

One should never, in even one's heart, do an injury to kine. One should, indeed, always confer happiness on them. One should always reverence kine and worship them, with bends of one's head. He who does this, restraining his senses the while and filled with cheerfulness, succeeds in attaining to that felicity which is enjoyed by kine (and which kine alone can confer). One should for three days drink the hot urine of the cow. For the next three days one should drink the hot milk of the cow. Having thus drunk for three days hot milk, one should next drink hot ghee for three days. Having in this way drunk hot ghee for three days, one should subsist for the next three days on air only. That sacred thing by whose aid the deities enjoy regions of felicity, that which is the most sacred of all sacred things, viz., ghee should then be borne on the head.[380] With the aid of ghee one should pour libations on the sacred fire. By making gifts of ghee, one should cause the Brahmana to utter benedictions on oneself. One should eat ghee and make gifts of ghee. As the reward of this conduct, one may then attain to that prosperity which belongs to kine. That man who, for a month, subsists upon the gruel of barley picked up every day from cow dung becomes cleansed of sins as grave as the slaughter of a Brahmana. After their defeat at the hands of the Daityas, the deities practised this expiation. It was in consequence of this expiation that they succeeded in regaining their position as deities. Verily, it was through this that they regained their strength and became crowned with success. Kine are sacred. They are embodiments of merit. They are high and most efficacious cleansers of all. By making gifts of kine unto the Brahmanas one attains to Heaven. Living in a pure state, in the midst of kine, one should mentally recite those sacred Mantras that are known by the name of Gomati, after touching pure water. By doing this, one becomes purified and cleansed (of all sins).