Full Idea
You ask what I seek from virtue? Virtue herself. For she has nothing better, she is herself her own reward.
Gist of Idea
I seek virtue, because it is its own reward
Source
Seneca the Younger (On the Happy Life [c.60], §09)
Book Reference
Seneca: 'Dialogues and Essays', ed/tr. Davie,John [Penguin 2007], p.93
A Reaction
Presumably this is the source of the popular saying that 'virtue is its own reward'. The trouble is that this doesn't seem a very persuasive thing to say to a sceptic who doubts whether being virtuous is worth the trouble.