Shatapatha Brahmana 1.1.1.22

1.1.1.22

atha tṛṇaiḥ paristṛṇāti | dvandvam pātrāṇyudāharati śūrpaṃ cāgnihotrahavaṇīṃ ca sphyaṃ ca kapālānica śamyāṃ cakṛṣṇājinaṃ colūkhalamusale dṛṣadupala taddaśa daśākṣarā vai virāḍvirāḍvai yajñastadvirājamevaitadyajñamabhisampādayatyatha yaddvandvaṃ dvandvaṃ vai vīryaṃ yadā vai dvau saṃ rabhete atha tadvīryam bhavati dvandvaṃ vai mithunam prajananam mithunamevaitatprajananaṃ kriyate

He now strews sacrificial grass all round (the fires), and fetches the utensils, taking two at a time, viz. the winnowing basket and the Agnihotra ladle, the wooden sword and the potsherds, the wedge and the black antelope skin, the mortar and the pestle, the large and the small mill-stones. These are ten in number; for of ten syllables consists the Virâg (metre), and radiant (virâg) also is the sacrifice: so that he thereby makes the sacrifice resemble the Virâg. The reason why he takes two at a time is, because a pair means strength; for when two undertake anything, there is strength in it. Moreover, a pair represents a productive copulation, so that a productive copulation (of those respective objects) is thereby effected.