Śatapatha Brāhmaṇa ("of a hundred paths") 6.4.4.6

6.4.4.6

athainameteṣām paśūnāmupariṣṭātpragṛhṇāti | tadenametaiḥ paśubhiḥ sambharati nopaspṛśati vajro vai paśavo reta idaṃ nedidaṃ reto vajreṇa hinasānītyatho agnirayam paśava ime nedayamagnirimānpaśūnhinasaditi

He then holds it (Agni, the lump of clay) over these animals, whereby he equips him (Agni) with these cattle. He does not touch them, lest he should injure that seed by the thunderbolt, for cattle are a thunderbolt, and this (clay) is seed; or lest that Agni should injure those cattle, for that (lump of clay) is Agni, and these (animals) are cattle.