Shatapatha Brahmana 13.6.1.1

13.6.1.1

puruṣo ha nārāyaṇo'kāmayata atitiṣṭheyaṃ sarvāṇi bhūtānyahamevedaṃ sarvaṃ syāmiti sa etam puruṣamedham pañcarātram yajñakratumapaśyattamāharattenāyajata teneṣṭvātyatiṣṭhatsarvāṇi bhūtānīdaṃ sarvamabhavadatitiṣṭhati sarvāṇi bhūtānīdaṃ sarvam bhavati ya evam vidvānpuruṣamedhena yajate yo vaitadevam veda

Purusha Nârâyana desired, 'Would that I overpassed all beings! would that I alone were everything here (this universe)!' He beheld this five-days’ sacrificial performance, the Purushamedha, and took it, and performed offering therewith; and having performed offering therewith, he overpassed all beings, and became everything here. And, verily, he who, knowing this, performs the Purushamedha, or who even knows this, overpasses all beings, and becomes everything here.