The fifteenth chapter of the Bhagavad Gita, traditionally titled the Purushottama Yoga, has Krishna set out a threefold hierarchy of being that gives the Mahapurusha concept its clearest scriptural statement: below stands the perishable, kshara, the whole of embodied material existence subject to change and decay, above that stands the imperishable, akshara, the unchanging individual self or soul, and beyond both, Krishna declares, stands a third and highest reality, the Purushottama, the Supreme Person, who pervades and sustains the other two while remaining untouched by either's limitations. This move deliberately goes beyond the older Samkhya framework's simpler dualism of purusha, consciousness or self, and prakriti, matter, by inserting a supreme instance of personhood above the generic individual purusha, and Krishna states plainly that whoever realizes him in this highest aspect knows all there is to know and worships him with their whole being, collapsing the distinction philosophy might otherwise draw between metaphysical knowledge and devotional practice.
Vaishnava commentators across the following centuries, including the major theologians of the Vedanta schools who wrote extensive commentaries on this exact passage, treated it as scriptural warrant for identifying their supreme deity, Vishnu or Krishna depending on the specific tradition, as this highest, all-encompassing Person rather than as merely one god among the pantheon's many purushas.