Shatapatha Brahmana 8.5.4.1

8.5.4.1

tā aṣāḍhāyai velayopadadhāti | vāgvā aṣāḍhā rasa eṣa vāci tadrasaṃ dadhāti tasmātsarveṣāmaṅgānāṃ vācaivānnasya rasaṃ vijānāti

He lays them down on the range of the Ashâdhâ; for the Ashâdhâ is speech, and this (set of bricks) is the essence (of food): he thus lays into speech the essence of food; whence it is through (the channel of) speech that one distinguishes the essence of food for all the limbs.