Śatapatha Brāhmaṇa ("of a hundred paths") 5.4.2.10

5.4.2.10

atha ya eṣa saṃsravo 'tirikto bhavati tamāgnīdhrīye juhotyatirikto vā eṣa saṃsravo bhavatyatirikta āgnīdhrīyo gārhapatye havīṃṣi śrapayantyāhavanīye juhvatyathaiṣo 'tiriktaṃtadatirikta evaitadatiriktaṃ dadhātyuttarārdhe juhotyeṣa hyetasya devasya diktasmāduttarārdhe juhoti sa juhoti rudra yatte krivi paraṃ nāma tasminhutamasyameṣṭamasi svāheti

And any residue that is left over, he offers in the Âgnîdhrîya; for redundant is that residue, and redundant also is the Âgnîdhrîya,--in the Gârhapatya they cook the oblations, and in the Âhavanîya they offer, but that one is redundant: thus he puts the redundant to the redundant. He offers it on the north part (of the hearth), for that is the region of that god (Rudra): hence he offers it on the north part. He offers with, 'O Rudra, whatever potent, highest name is thine, therein thou art an offering, thou art a home-offering, hail!'