The more you're honoring Shabbat... Welcome to the Daily Halacha. There are three mitzvot (commandments) a person has a chance to do, the Kevod Shabbat Kodesh—specifically for Shabbat. One is taking a hot shower. Two is taking a haircut: hair on the head or on the face, like a beard. And three is cutting your nails, whether your fingernails or your toenails. Three specific mitzvot.
Now, a question came up. Shabbat starts much earlier on Friday afternoon, and people are busy at work, so when they come home, they don't have that much time to jump into the shower before Shabbat. So what's the earliest time one can shower Lichvod Shabbat Kodesh in honor of Shabbat? The answer is that Hacham Ovadia brings down that the earliest time when, if you shower, it's considered that you're doing it for the mitzvah of Shabbat is Thursday afternoon. So Thursday afternoon is the earliest time during the day. If you can't do it then, Thursday night; if you can't do it then, Friday morning. And if you can do it later, like Friday afternoon, it's much better. The closer you are doing it to Shabbat—to the time of Shabbat—the more obvious it is that you're doing it for the mitzvah of honoring Shabbat. So the bigger mitzvah it is. Now, obviously, be careful: don't shower right before Shabbat, says Hacham Ovadia, because it can lead to coming late to candle lighting, which is not good. So obviously he said, “Be smart with your time.” But the rule is that the closer you are doing the shower before Shabbat, the more obvious it is that you're doing it for Shabbat, the more of a mitzvah it is. But if you can't do it then, you can do it Friday morning, Thursday night. But you have to have in mind, “I'm doing Lichvod Shabbat Kodesh.”
An interesting question that Hacham Ovadia discusses is: Let's say a person had to take a shower Friday morning because he got dirty. Let's say he works as a plumber. Or let's say a person went to the pool, to a public, and then afterward he had to shower to clean himself. So he jumps in the shower. If he didn't have in mind, “I'm doing Lichvod Shabbat Kodesh,” those showers are not necessarily considered a mitzvah to honor Shabbat, because he was going to take the shower because he had just left the pool Friday morning, or he had just left his job that he had to do Friday morning. So they might have to go into the shower again, with hot water, in order to do a mitzvah shower for Shabbat. But if you have in mind that “I'm showering Lichvod Shabbat Kodesh,” then even though you're jumping into the shower right after the pool, it's also a mitzvah. You have to have that in mind.