SB 1.3 - Kṛṣṇa superior to the puruṣa
In Chandogya Upaniṣad (3.12.6) the puruṣa is said to be greater than Brahman. In 3.14.1 it said everything is Brahman. After these descriptions of Brahman and the puruṣa, Ghora Aṅgirasa in 3.17.6 says to Kṛṣṇa, the son of Devakī, that at the moment of death a knower of Brahman should meditate on the following truths: ‘Thou art the imperishable’, ‘Thou art the changeless reality’ and ‘Thou art the source of life or the essence of prāṇa’. This highest knowledge of Brahman, having drunk of which one never thirsts again, was said by Ghora to Kṛṣṇa. This implies that the knower of Brahman should meditate on Kṛṣṇa being the imperishable, the changeless and source of life because Ghora is addressing Kṛṣṇa with the word ‘Thou’. Viśvanātha Cakravartī quotes Chandogya 3.12.6 and 3.14.1 and then says everything is summarized by saying kṛṣṇāya devakī-putrāya: the puruṣa is subservient to Kṛṣṇa, the son of Devakī. (There are some who do not accept this verse as referring to Lord Kṛṣṇa since it seems like Ghora Aṅgirasa is instructing Kṛṣṇa to meditate on the three statements, with the ‘Thou’ referring to Brahman).
The Bṛhad-āraṇyaka Upaniṣad (1.4.1) says ‘ātmaivedam agra āsīt puruṣa-vidhaḥ’ indicating that Kṛṣṇa existed even before the appearance of the puruṣa incarnation. In Bhagavad gītā (15.18) Kṛṣṇa says that He is superior to puruṣa-kṣara and puruṣa-akṣara. The akṣara-puruṣa or Mahā-Viṣṇu throws His glance over prakṛti, but the Puruṣottama existed even before that.