I believe with virtually all CCs you get the points you earned, even if you pay it off early. You won't get the rewards until the statement is complied in most cases though.
However, I think I've gotten a couple offers in the mail years ago that only give cash back on the interest you pay. Pay in 19% interest and we'll give you 5% cash back. Yeah, a nice -14% there. :roll: If you happen to have one of those scam cards, you wouldn't pay interest and then you wouldn't get a small fraction of that interest back. If that is the case, get rid of the card.
That said, why pay it off early? Keep that $42 in your account earning interest until they complile the statement. Then pay it off in full.