Well, you can commit a sin...but can you "commit a virtue"???
Whitman...exactly.... A sin is an act of intent or omission, while a virtue is attributed to a "Good Deed".
This topic has made me think quite a lot (and reminisce) about that "old time religion", that RC upbringing that renders one guilt-ridden. The concept of sin is just our inherent nature to lean towards evil...when we quell or resist that urge our virtue shows - there should be a word for this!!!
And I Heartily agree with the "mitzvah" concept since Judaism is based on "good deeds" - the positive is reinforced more than the "Thou shalt not...."