The Puruṣa of this hymn did not stay in the Ṛgveda. The Upaniṣads, the Gītā and the devotional traditions all return to him, and each sees something new.
“Puruṣa is all this”
The Śvetāśvatara Upaniṣad (3.14–15) quotes the first two verses almost word for word: sahasraśīrṣā puruṣaḥ … puruṣa evedaṃ sarvam. Just before, it says that this same Puruṣa, “the size of a thumb, dwells always in the heart of beings” (3.13). The Puruṣa who exceeds the earth by ten fingers is also the inner self.
The Self in the form of a person
The Bṛhadāraṇyaka Upaniṣad (1.4.1) begins one of its creation accounts: ātmaivedam agra āsīt puruṣavidhaḥ, “In the beginning this was the Self alone, in the form of a person.” The cosmic Puruṣa of the Ṛgveda has become the ātman, the Self.
The body and the gods, in reverse
The Aitareya Upaniṣad (1.1–2) retells the hymn’s verses 13 and 14 and then turns them around. From Puruṣa’s mouth comes speech, and from speech fire; from his eyes sight, and from sight the sun. Then the gods enter a human body: fire becomes speech and enters the mouth, the sun becomes sight and enters the eyes, the moon becomes mind and enters the heart. The cosmos is in us, as we are in it.
The universal form
In the eleventh chapter of the Bhagavad Gītā, Arjuna is shown Kṛṣṇa’s universal form: “with many mouths and eyes … with countless arms, bellies, faces and eyes” (11.10, 11.16), the whole universe gathered in one body. It is the thousand-headed Puruṣa seen face to face, terrifying and magnificent. The Gītā also says of the highest reality, “its hands and feet are everywhere, its eyes, heads and faces everywhere” (13.13), and it calls Kṛṣṇa puruṣottama, the highest Puruṣa (15.18).
Puruṣa in Sāṅkhya
In the Sāṅkhya philosophy, puruṣa takes a different meaning: the pure, witnessing consciousness, distinct from prakṛti, the world of matter and change. The word is the same, the idea is new: not the body of the world, but the one who watches it.
Nārāyaṇa and daily worship
Later tradition identifies Puruṣa with Nārāyaṇa, the hymn’s own seer, and with Viṣṇu. In temple and household worship the sixteen verses are often recited with the sixteen offerings (ṣoḍaśopacāra) made to the deity, one verse to each, from inviting the god to the final farewell. So the hymn about the first sacrifice is still, three thousand years later, the words of an offering.