Bhagavad Gita 6.12

तत्रैकाग्रं मन: कृत्वा यत्चित्तेन्द्रियक्रिय: |
उपविषयासने युञ्ज्यौद्योगमात्मविशुद्धये

Translation

Seated firmly on it, the yogi should strive to purify the mind by focusing it in meditation with one pointed concentration, controlling all thoughts and activities.