Mbh 13.104.2f

One should not answer a call of nature on a field (where crops are grown) or at a place too near an inhabited village. One should never answer a call of nature on a water. One should first wash one's mouth thrice with water before eating any food. Having finished one's meals, one should wash one's mouth thrice with water and twice again. One should eat, with face turned eastwards, one's food, restraining speech the while and without censuring the food that is eaten. One should always leave a remnant of the food that is placed before one for eating. Having finished one's meals, one should mentally touch fire. If one eats with face turned eastwards, one becomes endued with longevity. By eating with face turned southwards, one acquires great fame. By eating with face turned westwards, one acquires great wealth. By eating with face turned northwards, one becomes truthful in speech. Having finished one's meals one should wash all the upper holes of one's body with water.[465] Similarly, all the limbs, the navel, and the palms of the hands should be washed with water. One should never seat oneself upon husk of corn, or upon hair, or upon ashes, or upon bones. One should, on no account, use the water that has been used by another for bathing. One should always perform the Homa for propitiating the deities, and recite the Savitri Mantra. One should always eat in a seated posture. One should never eat while walking. One should never answer a call of nature in a standing posture. One should never answer a call of nature on ashes or in a cow-pen. One should wash one's feet before sitting to one's meals. One should never sit or lie down for sleep with wet feet. One who sits to one's meals after having washed one's feet, lives for a hundred years. One should never touch these three things of great energy, while one is in an impure state, viz., fire, a cow, and a Brahmana. By observing this rule, one acquires longevity.