Chapter 13 · verse 21 · gita.yoga.org

Bhagavad Gita 13.21

कार्यकारणकर्तृत्वे हेतुः प्रकृतिरुच्यते।पुरुषः सुखदुःखानां भोक्तृत्वे हेतुरुच्यते

In the production of the effect and the cause, Nature (matter) is said to be the cause; in the experience of pleasure and pain, the soul is said to be the one responsible.