Śatapatha Brāhmaṇa ("of a hundred paths") 7.2.1.5

7.2.1.5

yadvevaitā nairṛtīrharanti | prajāpatiṃ visrastaṃ yatra devāḥ samaskurvaṃstamukhāyāṃ yonau reto bhūtamasiñcanyonirvā ukhā tasmā etāṃ saṃvatsare pratiṣṭhāṃ samaskurvannimameva lokamayaṃ vai loko gārhapatyastasminnenam prājanayaṃstasya yaḥ pāpmā yaḥ śleṣmā yadulbaṃ yajjarāyu tadasyaitābhirapāghnaṃstadyadasyaitābhiḥ pāpmānaṃ nirṛtimapāghnaṃstasmādetā nairṛtyaḥ

And, again, why they take these (bricks) of Nirriti;--when the gods restored the relaxed Pragâpati, they cast him as seed into the fire-pan, the womb; the fire-pan being indeed a womb. In the course of a year they prepared for him this foundation, even this (terrestrial) world; the Gârhapatya (hearth) being this world: therein they generated him. And whatever evil there was in him, whatever mucus, whatever inner and outer membrane, that they removed from him by means of these (bricks); and inasmuch as thereby they removed his evil, his corruption, these are Nirriti's (bricks).