We need to start with a different question. Shabbat officially begins with the recitation of Psalm 92 – Mizmor Shir L’yom HaShabbat – at the conclusion of L’cha Dodi. After that, we recite Psalm 93, Hashem Malach Ge’ut Lavesh. But Psalm 93 is the “song of the day” for Friday! First of all, why is the song for Friday later in sequence than the song for Shabbat, and even if we can answer that, why at the beginning of Shabbat, when we do recite the song for Shabbat, do we then backtrack and repeat the song for Friday immediately afterward?

To understand this, we need to look at why Psalm 93 was selected as the song for Friday. The commentators say it is because “ge’ut lavesh” – “[the Almighty] dons grandeur” can serve as a reminder on Erev Shabbat of the special clothing we are to don in honor of Shabbat. What is the idea behind putting on special clothing for Shabbat? Interestingly, there is no obligation to wear ornate or fancy clothing on Shabbat; the obligation is to wear different clothing for Shabbat than you wear during the week – clothing dedicated for Shabbat use only. One explanation for this practice is in order to bring out the concept that we are different individuals on Shabbat than we are during the week. If we are different individuals, that necessitates our having a different wardrobe; hence the special clothes reserved only for the use of our “Shabbat selves”.

My problem with this explanation is that nobody waits until after Shabbat begins in order to don Shabbat clothing. When do we get dressed for Shabbat? Erev Shabbat! How can our weekday self be the one that is putting on our Shabbat clothing?

The explanation must be as follows:

On Friday, we recite Psalm 93 as a reminder to dress properly for Shabbat. The reason we dress in special clothes for Shabbat is indeed in order to reflect the fact that we become different people on Shabbat than who we are during the week. But that difference, as keenly as it may be felt internally, may be lost on others in the pageantry of the elegant clothing we are all wearing. And so, we dress in our Shabbos clothes BEFORE Shabbos begins – on Erev Shabbos. This way, observers who see us on Shabbos will have already seen us in those very same clothes before Shabbos started. Seeing us now, however, through Shabbos eyes, they will see how different we actually look in our Shabbos clothing with the onset of the kedusha of Shabbos.

This is the reason for reciting Psalm 93 after Psalm 92 on Friday night. Psalm 93 was the Friday song, reminding us to dress properly for Shabbat. But when we did so, it was still Friday and no one could see these garments helping to give us a Shabbos glow. After we recite Psalm 92 and everyone receives the sanctity of Shabbat, we repeat Psalm 93, as a way of inviting our observers to look again and see the distinction between the look of a Friday Jew wearing Shabbat clothing and the look of a Shabbos Jew.