। ॥ १८६ ॥
In plain words
The intellect, joined with the five knowing senses, with its own mental activity, wearing the mask of 'I am the doer' — this is the sheath of understanding. It is the very reason the individual soul keeps circling through birth and death.
Close to the Sanskrit
The intellect, together with the organs of knowledge, possessed of mental modifications, characterized by agency — this is the vijñānamaya kośa, the cause of the individual's transmigratory existence.