There are lots of opinions out there about whether or not you should run the day before a race, regardless of whether you're running a shorter race like a 5K or a long-distance event such as a marathon. On the one hand, it's good to rest your running muscles in preparation for a race, especially if it's a long one, such as a marathon. Most runners who rest the day before a race say that they feel fresh and ready when they get to the starting line. But other runners will swear by running very easy for 20 minutes the day before a race, saying that it helps them loosen up and shake off the nervous feelings.
So, you really need to see what works best for you. If you're the type of person who gets race anxiety, it might be beneficial for you to do a very slow, 20-minute jog the day before. But if you think you perform better on rest, then just relax during those 24 hours leading up to the race. Whatever you do, just make sure that you don't do a significant, hard workout, like a long run, speed workout, or strength training, that's going to leave you feeling tired or sore the next day.