Bhagavad Gita · 4.20

त्यक्त्वा कर्मफलासङ्गं नित्यतृप्तो निराश्रयः।कर्मण्यभिप्रवृत्तोऽपि नैव किञ्चित्करोति सः॥

tyaktvā karma-phalāsaṅgaṁ nitya-tṛipto nirāśhrayaḥ karmaṇy abhipravṛitto 'pi naiva kiñchit karoti saḥ

Having abandoned attachment to the fruits of action, ever content, depending on nothing external — such a person, even while fully engaged in action, does not truly do anything at all.

— Bhagavad Gita 4.20

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