Chapter 6 · verse 34 · gita.yoga.org

Bhagavad Gita 6.34

चञ्चलं हि मनः कृष्ण प्रमाथि बलवद्दृढम्। तस्याहं निग्रहं मन्ये वायोरिव सुदुष्करम्

The mind is indeed restless, turbulent, strong, and unyielding, O Krishna; I consider it as difficult to control as controlling the wind.