Dhammapada · 21.3

Yañhi kiccaṃ apaviddhaṃ, akiccaṃ pana kayirati;Unnaḷānaṃ pamattānaṃ, tesaṃ vaḍḍhanti āsavā.

Yanhi kiccam apaviddham, akiccam pana kayirati; Unnalanam pamattanam, tesam vaddhanti asava.

What should be done is left undone, while what should not be done is done — for the proud and the heedless, the cankers grow.

— Dhammapada 21.3

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.