Śatapatha Brāhmaṇa ("of a hundred paths") 7.3.2.4

7.3.2.4

tadāhuḥ | yatprathamāmeva citim prokṣati kathamasyaiṣa sarvo 'gniḥ prokṣito bhavati kathaṃ carmaṇi praṇītaḥ kathamaśvapraṇīta iti yadevātra sarvāsāṃ citīnāmiṣṭakāḥ prokṣatyevamu hāsyaiṣa sarvo 'gniḥ prokṣito bhavatyevaṃ carmaṇi praṇīta evamaśvapraṇīta udyacantyetāṃ citim

As to this they say, 'When he sprinkles only the first layer, how does that whole fire-altar of his come to be sprinkled, how does it come to be led forward on the skin, and how led forward by the horse?' Inasmuch as in this (layer) he (symbolically) sprinkles the bricks of all the layers; and thus indeed that whole fire-altar of his comes to be sprinkled, and led forward on the skin, and led forward by the horse. They lift up this (first) layer.