Śatapatha Brāhmaṇa ("of a hundred paths") 8.2.1.13

8.2.1.13

tadyā etāḥ pañcāśvinyaḥ | etadasya tadātmanastadyadetā atropadadhāti yadevāsyaitā ātmanastadasminnetatpratidadhāti tasmādetā atropadadhāti

Now these five Âsvinî (bricks) are that same (part) of his (Agni's) body; and when he now puts them into this (layer of the altar), he thereby restores to him what (part) of his body these (bricks) are: that is why he puts them into this (layer).