Shatapatha Brahmana 6.7.4.13

6.7.4.13

sa yadahaḥ saṃnivapsyantsyāt tadahaḥ prātarudita āditye bhasmaiva prathamamudvapati bhasmodupya vācaṃ visṛjate vācaṃ visṛjya samidhamādadhāti samidhamādhāya bhasmāpo 'bhyavaharati yathaiva tasyābhyavaharaṇaṃ tathāpādāya bhasmanaḥ pratyetyokhāyāmopyopatiṣṭhate 'tha prāyaścittī karoti

As to this they say, 'If the Vishnu-strides are the day, and the Vâtsapra the night, and both of them are (performed) during the day, not during the night, how then are they both performed for (or by) him also during the night?' Well, on that (first) occasion, when he is being initiated, he, at the outset, combines both (performances) in the afternoon; for the afternoon is the same thing as the night. Then throwing them thus together, he at the end combines them both in the forenoon; for the forenoon is the same thing as the day; and in this way they are both performed during the day, and both during the night.