Śrīmad-Bhāgavatam · Text 6.4.52
Who is speaking and story frame
मिथुनव्यवायधर्मस्त्वं प्रजासर्गमिमं पुन: ।
मिथुनव्यवायधर्मिण्यां भूरिशो भावयिष्यसि ॥ ५२ ॥
mithuna-vyavāya-dharmas tvaṁ
prajā-sargam imaṁ punaḥ
mithuna-vyavāya-dharmiṇyāṁ
bhūriśo bhāvayiṣyasi
Now unite in sexual life as man and woman, and in this way, by sexual intercourse, you will be able to beget hundreds of children in the womb of this girl to increase the population.
Read Śrīla Prabhupāda's purport on Vedabase.io