Chapter 18 · Liberation through Renunciation · Krishna said
Bhagavad Gita 18.16 — The illusion of sole doer
तत्रैवं सति कर्तारमात्मानं केवलं तु यः। पश्यत्यकृतबुद्धित्वान्न स पश्यति दुर्मतिः ॥
tatraivaṃ sati kartāramātmānaṃ kevalaṃ tu yaḥ | paśyatyakṛtabuddhitvānna sa paśyati durmatiḥ ||
Meaning
Yet one who, with an untrained mind, sees himself alone as the doer does not see the truth.