I don't know what that is, but it's not Spamassassin. I have SA installed, and I have no /usr/lib/sa or /var/log/sa directory.
I can see what's wrong with the command, the ( and ) should be escaped, as \( and \). As it is it's invalid shell syntax. It looks very odd though, because I don't know what /dev/rd/b is, and you wouldn't expect to invoke "find" under that path - it needs no qualifying as it's in one of the main bin directories.
Have a look at what files are in /etc/cron.daily, one of them must be kicking this off, should give you a clue.
Rick