Śatapatha Brāhmaṇa ("of a hundred paths") 13.8.1.8

13.8.1.8

dakṣiṇāpravaṇasya pratyarṣe kuryādityu haika āhuḥ tatpratyucritamagham bhavatīti no eva t!thā kuryādyadvā udīcīnapravaṇe karoti tadeva pratyucritamagham bhavati

And some, indeed, say, 'Let him make it on a counter-cutting in ground inclined towards the south, for such (a tomb) indeed becomes rising sin.' But one must not do so, for indeed such (a burial place) alone becomes rising sin which one makes, on ground inclining towards the north.