Śatapatha Brāhmaṇa ("of a hundred paths") 7.4.1.36

7.4.1.36

atha srucā upadadhāti | bāhū vai srucau bāhū evāsminnetatpratidadhāti te yatsrucau bhavataḥ srucau hi bāhū idameva kapucalamayaṃ daṇdo dve bhavato dvau hīmau bāhū pāśvata upadadhāti pārśvato hīmau bāhū

He then lays down two offering-spoons,--the offering-spoons are arms: it is his arms he thus restores to him (Agni). And as to why offering-spoons (are laid down), it is because the arms are offering-spoons,--that bowl and the handle are two, for there are two of these arms. He lays them down at the (left and right) sides, for these arms (of ours) are at the sides.