Bhagavad Gita 2.41
By its means, the straying intellect becomes steadied in contemplating one object only; whereas the minds of the irresolute stray into innumerable bypaths.
व्यवसायात्मिका बुद्धिरेकेह कुरुनन्दन।
बहुशाखा ह्यनन्ताश्च बुद्धयोऽव्यवसायिनाम्॥vyavasāyātmikā buddhirekeha kurunandana|
bahuśākhā hyanantāśca buddhayo'vyavasāyinām||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).