Śatapatha Brāhmaṇa ("of a hundred paths") 4.3.5.17

4.3.5.17

taṃ na daśābhirna pavitreṇopaspṛśati ete vai śukravatī rasavatī savane yatprātaḥsavanaṃ ca mādhyandinaṃ ca savanamathaitannirdhītaśukraṃ yattṛtīyasavanaṃ sa yanna daśābhirna pavitreṇopaspṛśati teno hāsyaitacukravadrasavattṛtīyasavanam bhavati tasmānna daśābhirna pavitreṇopaspṛśati

He touches it neither with the fringe nor with (the woven part of) the straining-cloth; for those two pressings, the morning pressing and midday pressing, forsooth are rich in pure Soma, rich in juice, but this, the third pressing, is emptied of its pure Soma. Now, in that he does not touch it either with the fringe or the straining-cloth, thereby that third pressing of his also becomes rich in pure Soma and juice: therefore he touches it neither with the fringe nor with the straining-cloth.