Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.2.2

2.6.2.2

atha yadeṣa etairyajate | tannāha nvevaitasya tathā kaṃ caneṣurṛcatīti devā akurvanniti tvevaiṣa etatkaroti yāśca tvevāsya prajā jātā yāścājātāstā ubhayī rudriyātpramuñcati tā asyānamīvā akilviṣāḥ prajāḥ prajāyante tasmādvā eṣa etairyajate

And, accordingly, when he performs those offerings, he either does so hoping that thus no arrow (misfortune) will hit any of his, or because the gods did so. And thereby he delivers from Rudra's power both the descendants that are born unto him and those that are unborn; and his offspring is brought forth without disease and blemish. This is why he performs these offerings.