Śatapatha Brāhmaṇa ("of a hundred paths") 3.3.2.18

3.3.2.18

atha yaddaśa kṛtvo mimīte | daśākṣarā vai virāḍvairājaḥ somastasmāddaśa kṛtvo mimīte

Having gathered up the ends of the Soma-cloth, he (the Adhvaryu) ties them together by means of the head-band, with, 'For descendants (I tie) thee;'--for it is indeed for (the purpose of obtaining) descendants that he buys it (Soma): what (part of man) here is, as it were, compressed between the head and the shoulders, that he thereby makes it to be for him (the sacrificer).