Manava Dharmashastra 6.96

6.96

svakāryamātmopāsanaṃ paramaṃ pradhānamasyeti svakāryaparamaḥ | aspṛhaḥ manasā'pi spṛhā na kvacitkartavyā |

Medhātithi’s commentary (manubhāṣya):
‘His oven duty’—meditation on the Soul; he for whom this is the highest duty.

‘Free from longings’—not entertaining a desire for anything, even in his mind—(96).