Śrīmad-Bhāgavatam · Text 3.12.4
Who is speaking and story frame
सनकं च सनन्दं च सनातनमथात्मभू: ।
सनत्कुमारं च मुनीन्निष्क्रियानूर्ध्वरेतस: ॥ ४ ॥
sanakaṁ ca sanandaṁ ca
sanātanam athātmabhūḥ
sanat-kumāraṁ ca munīn
niṣkriyān ūrdhva-retasaḥ
In the beginning, Brahmā created four great sages named Sanaka, Sananda, Sanātana and Sanat-kumāra. All of them were unwilling to adopt materialistic activities because they were highly elevated due to their semen’s flowing upwards.
Read Śrīla Prabhupāda's purport on Vedabase.io