Chapter 2 · The Yoga of Knowledge · Krishna said
Bhagavad Gita 2.67 — Boat in the wind
इन्द्रियाणां हि चरतां यन्मनोऽनुविधीयते। तदस्य हरति प्रज्ञां वायुर्नावमिवाम्भसि ॥
indriyāṇāṃ hi caratāṃ yanmano'nuvidhīyate | tadasya harati prajñāṃ vāyurnāvamivāmbhasi ||
Meaning
Just as wind carries a boat away on water, even one wandering sense that the mind follows can carry away a person's understanding.