Bhagavad Gita · 2.67

इन्द्रियाणां हि चरतां यन्मनोऽनुविधीयते।तदस्य हरति प्रज्ञां वायुर्नावमिवाम्भसि॥

indriyāṇāṁ hi charatāṁ yan mano 'nuvidhīyate tad asya harati prajñāṁ vāyur nāvam ivāmbhasi

When the mind follows the wandering senses, it carries away one's wisdom, as the wind carries away a boat on the water.

— Bhagavad Gita 2.67

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)