That highest Purusha, O Arjuna, is attainable by unswerving devotion to Him alone within Whom all beings dwell and by Whom all this is pervaded.
In simple words
Krishna tells Arjuna how to reach it: "That supreme being — in whom all living things exist and who fills everything — is reached through single-minded, unwavering devotion."
Contemporary scholarly and practical interpretations for modern seekers.
Swami Sivananda
8.22 पुरुषः Purusha? सः that? परः highest? पार्थ O Partha? भक्त्या by devotion? लभ्यः is attainable? तु verily? अनन्यया without another object (unswerving)? यस्य of whom? अन्तःस्थानि dwelling within? भूतानि beings? येन by whom? सर्वम् all? इदम् this? ततम् pervaded.Commentary All the beings (effects) dwell within the Purusha (the Supreme Person? the cause) because every effect rests within its cause. Just as the effect? pot? rests within its cause? the clay? so also all beings and the worlds rest within their cause? the Purusha. Therefore the whole world is pervaded by the Purusha.Sri Sankara explains exclusive devotion as Jnana or knowledge of the Self.Purusha is so called because everything is filled by It (derived from the Sanskrit root pur which means to fill) or because It rests in the body of all (derived from the Sanskrit root pur). None is higher than It and so It is the Supreme Person. (Cf.IX.4XI.38XV.6and7)
Swami Chinmayananda
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
The Lord Sri Krishna, the Teacher of the Hindus, here reveals the path of practice through which the Supreme Person may be attained—that Supreme Person who was spoken of as the unmanifest, imperishable Brahman. That path is unwavering devotion.
True and complete devotion to the Supreme Person arises only when the seeker-devotee learns to withdraw and detach themselves from the world as perceived through body, mind, and intellect. Love for the eternal, transcendent Truth is the very means by which dispassion toward the false arises. The search for the Self, animated by keen inquiry, and the subsequent realization of unity with it—the recognition "This Self am I"—this is the unwavering devotion spoken of here.
The Self, realized through a mind absorbed in meditation as one's own true nature, should not be understood as a limited conscious principle confined to a single individual limitation, bestowing consciousness only within that boundary. Though the seeker discovers and experiences the Self within their own heart, their knowledge becomes this: that this conscious Self is the foundation of the entire universe. The Lord Sri Krishna points to the unity of this heart-dwelling Self with the eternal Brahman through these words: That Person in whom all beings dwell, and by whom this entire universe is pervaded—He is the Supreme.
All pots made of clay rest in clay itself, and though their names, forms, colors, and shapes vary, one clay alone pervades them all. All waves, ripples, and foam rest in the ocean alone, and the ocean pervades them. Within and without the pots, their material cause—their essential nature—is clay; in the waves, it is the ocean.
Pure consciousness itself is that eternal Truth in which the unmanifest creation becomes manifest. The pattern drawn with thread upon cloth has cotton as its foundation; without it, that pattern could not exist. The pure conscious principle, molded into the various forms of desire, takes on gross form through ignorance, and appears as the countless-named, countless-formed universe. Thereafter, everywhere, all beings are drawn to objects upon seeing them, desire them, and struggle to obtain them. The person who directly realizes the nature of the Self understands this: that this manifold creation has but one foundation, and it is through ignorance of this that the world appears as real. The individual, enslaved by ignorance, takes this to be truth and remains afflicted by the false sufferings of existence.
After revealing the two distinct paths of return from the manifest to the unmanifest, the Lord now, in the next section, describes the two different destinations that may be attained by seekers, and the different paths to each. Some seekers attain that destination from which the world returns again and again; the other destination is such that, having attained it, one need not return to the world again.
What are these two paths? The Lord speaks: