Śatapatha Brāhmaṇa ("of a hundred paths") 6.4.4.20

6.4.4.20

athainaṃ viṣyati | tadyadevāsyātropanaddhasya saṃśucyati tāmevāsmādetacucam bahirdhā dadhātyatho etasyā evainametadyoneḥ prajanayati

He then unties it (the lump of clay): whatever part of his (body) pains him (Agni) when tied up, that pain he now puts outside of him; and, moreover, he causes him to be born from that womb (the antelope skin).