hetuḥ prakṛtir ucyate
bhoktṛtve hetur ucyate
kārya — of effect; kāraṇa — and cause; kartṛtve — in the matter of creation; hetuḥ — the instrument; prakṛtiḥ — material nature; ucyate — is said to be; puruṣaḥ — the living entity; sukha — of happiness; duḥkhānām — and distress; bhoktṛtve — in enjoyment; hetuḥ — the instrument; ucyate — is said to be.
Nature is said to be the cause of all material causes and effects, whereas the living entity is the cause of the various sufferings and enjoyments in this world.
. . .
कार्यकारणकर्तृत्वे हेतु: प्रकृतिरुच्यते ।
पुरुष: सुखदु:खानां भोक्तृत्वे हेतुरुच्यते ॥ २१ ॥