Śatapatha Brāhmaṇa ("of a hundred paths") 1.3.4.11

1.3.4.11

tatprastaraṃ stṛṇāti | ūrṇamradasaṃ tvā stṛṇāmi svāsasthaṃ devebhya iti sādhuṃ devebhya ityevaitadāha yadāhorṇamradasaṃ tveti svāsasthaṃ devebhya iti svāsadaṃ devebhya ityevaitadāha

On them he spreads the prastara, with the formula (Vâg. S. II, 5), 'I spread thee, soft as wool, pleasant to sit upon for the gods!' When he says 'thee, soft as wool,' he means to say 'agreeable to the gods;' and by 'pleasant to sit upon for the gods' he means to say 'forming a good seat for the gods.'