Manava Dharmashastra 2.2

2.2

kāmātmatā na praśastā na caivehāsty akāmatā
kāmyo hi vedādhigamaḥ karmayogaś ca vaidikaḥ //

To act solely from a desire for rewards is not laudable, yet an exemption from that desire is not (to be found) in this (world): for on (that) desire is grounded the study of the Veda and the performance of the actions, prescribed by the Veda.