Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 38


मयैतदुक्तं वो विप्रा गुह्यं यत् साङ्ख्ययोगयो: ।जानीत मागतं यज्ञं युष्मद्धर्मविवक्षया ॥ ३८ ॥


mayaitad uktaṁ vo viprāguhyaṁ yat sāṅkhya-yogayoḥjānīta māgataṁ yajñaṁyuṣmad-dharma-vivakṣayā


My dear brāhmaṇas, I have now explained to you the confidential knowledge of Sāṅkhya, by which one philosophically distinguishes matter from spirit, and of aṣṭāṅga-yoga, by which one links up with the Supreme. Please understand that I am the Supreme Personality of Godhead, Viṣṇu, and that I have appeared before you desiring to explain your actual religious duties.


To increase the faith of Lord Brahmā’s sons and establish the prestige of His teachings, Lord Kṛṣṇa now formally identifies Himself as the Supreme Personality of Godhead, Viṣṇu. As stated in Vedic literature, yajño vai viṣṇuḥ. After explaining the sāṅkhya- and aṣṭāṅga-yoga systems, the Lord clearly answers the original question of the sages, “Who are You, sir?” Thus, Lord Brahmā and his sons were enlightened by Lord Haṁsa.