In this verse it is clearly stated that the eternal, blissful, cognizant form of the Supreme Lord is to be found within the glaring effulgence of the brahmajyoti, which emanates from the body of the Supreme Lord. Thus the personal body of the Lord is the source of the brahmajyoti, as confirmed in the Bhagavad-gītā (14.27). That the impersonal Brahman is dependent on the Supreme Personality is also stated in the Hayaśīrṣa-pañcarātra. In every other Vedic scripture, such as the Upaniṣads, whenever there is talk of the impersonal Brahman in the beginning, the Supreme Personality is finally established at the end. The Īśopaniṣad mantra we cited above indicates that the Supreme Absolute Truth is both impersonal and personal eternally, but that His personal aspect is more important than the impersonal one.
According to a mantra in the Taittirīya Upaniṣad—yato vā imāni bhūtāni jāyante—this cosmic manifestation is an emanation from the Supreme Absolute Truth and it rests in the Supreme Absolute Truth. Thus the Absolute Truth has been called the ablative, causative and locative performer, and as such He must be the Supreme Personality of Godhead, for these are symptoms of personality. As the ablative performer, He is the source of all thinking, feeling and willing in this cosmic manifestation. Without thinking, feeling and willing, there is no possibility of the arrangement and design of the cosmic manifestation. Then again, He is causative, for He is the original designer of the cosmos. And He is also locative: that is, everything is resting in His energy. These attributes are all clearly attributes of His personality.