Link to purport by A C Bhaktivedanta Swami Srila Prabhupada

Transcript of Bhakti-Shastri class on this verse by Chaitanya Charan

Now the next subsection:

14.3-14.4: How the soul contacts matter

Bg 14.3

mama yonir mahad brahma
tasmin garbhaṁ dadhāmy aham
sambhavaḥ sarva-bhūtānāṁ
tato bhavati bhārata

Synonyms: 

mama — My; yoniḥ — source of birth; mahat — the total material existence; brahma — supreme; tasmin — in that; garbham — pregnancy; dadhāmi — create; aham — I; sambhavaḥ — the possibility; sarva–bhūtānām — of all living entities; tataḥ — thereafter; bhavati — becomes; bhārata — O son of Bharata.

Translation: 

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 son of Bharata.

mama yonir mahad brahma, here Krishna is using Brahma to material nature, same words can have different meanings, 

This brahma is the yoni in which I give garbha, tasmin garbhaṁ dadhāmy aham, I give the seed from which the womb is formed pregnancy takes place, the impregnation happens  

sambhavaḥ sarva-bhūtānāṁ, sambhavaḥ, to manifest, become possible all living beings 

tato bhavati bhārata, so here what Krishna is telling what is the connection 

Krishna has glorified the knowledge in previous two verses, He has caught Arjuna’s attention this knowledge is so important that it will make one free from of birth and death.

So soul are born from material nature but their source is not material nature as SP gave example of scorpion come out from rice. So main point in this verse is material nature doesn’t become active by its own.

End of transcription.