Śrīmad-Bhāgavatam · Text 10.3.33
Who is speaking and story frame
युवां वै ब्रह्मणादिष्टौ प्रजासर्गे यदा तत:
।
सन्नियम्येन्द्रियग्रामं तेपाथे परमं तप: ॥ ३३ ॥
yuvāṁ vai brahmaṇādiṣṭau
prajā-sarge yadā tataḥ
sanniyamyendriya-grāmaṁ
tepāthe paramaṁ tapaḥ
When both of you were ordered by Lord Brahmā to create progeny, you first underwent severe austerities by controlling your senses.
Read Śrīla Prabhupāda's purport on Vedabase.io