Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.22

2.5.2.22

tāni vai pratipuruṣam | yāvanto gṛhyāḥ syutāvantyekenātiriktāni bhavanti tatpratipuruṣamevaitadekaikena yā asya prajā jātāstā varuṇapāśātpramuñcatyekenātiriktāni bhavanti tadyā evāsya prajā ajātāstā varuṇapāśātpramuñcati tasmādekenātiriktāni bhavanti

Of these (dishes) there is one for each descendant; as many (children) as there are in the (sacrificer's) family, so many (dishes) there are, exceeded by one. There being one for each descendant, he thereby delivers from Varuna's noose one by one the children born to him; and there being an additional one, he thereby delivers from Varuna's noose those children of his that are as yet unborn: this is why there are (the same number of dishes) exceeded by one.