Shatapatha Brahmana 10.4.2.23

10.4.2.23

sa ṛco vyauhat dvādaśa bṛhatīsahasrāṇyetāvatyo harco yāḥ prajāpatisṛṣṭāstāstriṃśattame vyūhe paṅktiṣvatiṣṭhanta tā yattriṃśattame vyūhe'tiṣṭhanta tasmāttriṃśanmāsasya rātrayo'tha yatpaṅktiṣu tasmātpāṅktaḥ prajāpatistā aṣṭāśataṃ śatāni paṅktayo'bhavan

He arranged the Rik-verses into twelve thousand of Brihatîs, for of that extent are the verses created by Pragâpati. At-the thirtieth arrangement they 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' (fivefold). There are one hundred-and-eight hundred Paṅktis.