Sridhara Swami's Commentary
Responding in regard to Arjunas queries about control of the mind, Lord Krishna states that the mind is almost impossible to control; yet by constant practice, abdication from sense objects by dispassion and repeated meditation on the atma or soul it is possible to restrain and control the mind. With the senses withdrawn, being free from the obstacles of lethargy and distractions by means of incessant practice and dispassion, the mind remains immersed in the Supreme Self. It is stated in the Vedic scriptures that the tranquil mind in equanimity resides in the Brahman or spiritual substratum pervading all existence. Free from all conceptions and modifications is what is known as samadhi.