Bhagavad Gita: Chapter 2, Verse 68

तस्माद्यस्य महाबाहो निगृहीतानि सर्वशः ।
इन्द्रियाणीन्द्रियार्थेभ्यस्तस्य प्रज्ञा प्रतिष्ठिता ॥ २-६८ ॥

tasmād yasya mahā-bāho nigṛhītāni sarvaśaḥ
indriyāṇīndriyārthebhyas tasya prajñā pratiṣṭhitā 2.68

Therefore, O mighty-armed, one whose senses are restrained from their objects is certainly of steady intelligence.