The Lord impregnates Brahman in the form of the material nature with the seed of Brahman known as the jīva. As Kṛṣṇa says in the Bhagavad-gītā (14.3),
- mama yonir mahad brahma
- tasmin garbhaṁ dadhāmy aham
- sambhavaḥ sarva-bhūtānāṁ
- tato bhavati bhārata
The total material substance, called Brahman, is the source of birth, and it is that Brahman that I impregnate, making possible the births of all living beings, O scion of Bharata.
This verse explains the famous saying sarvaṁ khalv idaṁ brahma from the Upaniṣads, meaning "Everything is Brahman." In other words, the Supreme Brahman, Lord Kṛṣṇa, is identical with both the jīva and prakṛti in that they are all Brahman.