Shatapatha Brahmana 10.4.2.24

10.4.2.24

athetarau vedau vyauhat dvādaśaiva bṛhatīsahasrāṇyaṣṭau yajuṣāṃ catvāri sāmnāmetāvaddhaitayorvedayoryatprajāpatisṛṣṭaṃ tau triṃśattame vyūhe paṅktiṣvatiṣṭhetāṃ tau yattriṃśattame vyūhe'tiṣṭhetāṃ tasmāttriṃśanmāsasya rātrayo'tha yatpaṅktiṣu tasmātpāṅktaḥ prajāpatistā aṣṭāśatameva śatāni paṅktayo'bhavan

He then arranged the two other Vedas into twelve thousand Brihatîs,--eight (thousand) of the Yagus (formulas), and four of the Sâman (hymns)--for of that extent is what was created by Pragâpati in these two Vedas. At the thirtieth arrangement these two came to an end in the Paṅktis; and because it was at the thirtieth arrangement that they came to an end, there are thirty nights in the month; and because it was in the Paṅktis, therefore Pragâpati is 'pâṅkta.' There were one hundred-and-eight hundred Paṅktis.