SB 4.29.16
antah-puram ca hrdayam
visucir mana ucyate
tatra moham prasadam va
harsam prapnoti tad-gunaih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The word antah-pura refers to the heart. The word visucina, meaning “going everywhere,” indicates the mind. Within the mind the living entity enjoys the effects of the modes of material nature. These effects sometimes cause illusion, sometimes satisfaction and sometimes jubilation.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The mind and intelligence of the living entity in material existence are affected by the modes of material nature, and according to the association of the material modes, the mind is habituated to go here and there. The heart feels satisfaction, jubilation or illusion according to the effects of the modes of material nature. Actually the living entity in his material condition remains inert. It is the modes of material nature that act on the mind and heart. The results are enjoyed or suffered by the living entity. This is clearly stated in Bhagavad-gita (3.27):
prakrteh kriyamanani
gunaih karmani sarvasah
ahankara-vimudhatma
kartaham iti manyate
“The bewildered spirit soul, under the influence of the three modes of material nature, thinks himself the doer of activities that are in actuality carried out by nature.”