Full Idea
None of the virtues can exist unless they are disinterested, for virtue driven to duty by pleasure as a sort of pay is not virtue at all but a deceptive sham and pretence of virtue.
Gist of Idea
Virtues must be very detached, to avoid being motivated by pleasure
Source
M. Tullius Cicero (Academica [c.45 BCE], II.xlvi.140)
Book Reference
Cicero: 'De Natura Deorum and Academica (XIX)', ed/tr. Rackham,H. [Harvard Loeb 1933], p.649