Srimad Bhagavat Gita commentary chapter 13 verse 20

 Chapter 13 verse 20 

“Know that prakṛiti (material nature) and puruṣh (the individual souls) are both beginningless. Also know that all transformations of the body and the three modes of nature are produced by material energy.” 

Bhagwan has answered Arjuna’s questions on Kshetra, Kshetrajna and true knowledge. He now goes on to answer the last question, what is prakriti and purusha and difference between the same? Bhagwan explains that prakriti is the material energy, purusha is the individual soul of all the beings which represents a part of the spiritual energy of the supreme being-parama purusha. Since both energies are part of His whole, they have no beginning. Bhagwan also calls out the transformational and temporary nature of the material energy which is prakriti- insentient existence of the material nature.  The body and the associated 3 gunas-sattva, rajas and tamas all are representative of the material energy which is prakriti.