Garudapurana 3.12.1

3.12.1

śrīgaruḍamahāpurāṇam- 12
śrīkṛṣṇa uvāca /
nāḍīṃ samāviśya mahānubhāvaḥ śrīviṣṇubhakto tvatha puṣkarasthaḥ /
vicārayāmāsa guruṃ svamūlaṃ nārāyaṇaṃ nirguṇamadvitīyam //

The glorious Garuḍa Mahāpurāṇa, [Chapter] 12.
Śrī Kṛṣṇa said:
Having entered the stalk, that exalted devotee of glorious Viṣṇu, seated on the lotus, / investigated his teacher, his own root source, Nārāyaṇa, devoid of material qualities, without a second.