Dhammapada · 3.1

Phandanaṃ capalaṃ cittaṃ, dūrakkhaṃ dunnivārayaṃ;Ujuṃ karoti medhāvī, usukārova tejanaṃ.

phandanam capalam cittam, durakkham dunnivarayam; ujum karoti medhavi, usukaro-va tejanam.

The mind is restless, unsteady, hard to guard, hard to restrain. The wise one straightens it as a fletcher straightens an arrow shaft.

— Dhammapada 3.1

Source: Pali text from the Khuddaka Nikāya of the Pali Canon (oldest extant Buddhist scripture, compiled c. 3rd century BCE). Public-domain English readings drawn from F. Max Müller's translation in Sacred Books of the East, Vol X (1881) and the Buddhist Publication Society's freely-licensed Acharya Buddharakkhita rendering.