The Temple is gone and so are the offerings. Why do I still say the Levites' song?
It was never made a requirement. Peninei Halakhah (a modern guide to Jewish law by Rabbi Eliezer Melamed) says the Song of the Day was not set up as an obligation, and some people did not say it. By the end of the Middle Ages, everyone did.
Rambam (Maimonides, a great medieval codifier of Jewish law, who died in 1204) shows how loose it was. In his version of the prayer service he writes that "some of the people" had the custom of reading, after the supplications, the psalm the Levites said that day in the Temple.
So why do it? Tractate Soferim (an early medieval tractate about scribes and synagogue customs) gives one reason. One sage asks another whether the song may be said without the wine offering. The answer points to the Levites who sang when the Temple fell. Then it says people took on the custom of saying the psalms in their time, because whoever says a verse at its proper time is counted as if he built a new altar and offered a sacrifice on it.
Seder HaYom (a book of customs printed in 1599, by Rabbi Moshe ben Machir, who lived near Tzfat) gives a different reason. We say the Levites' song to remember the destruction of the Temple, to feel worried about it, and to ask God to give back the crown as it was and renew our days as in the past.
These two reasons pull in different directions. Soferim treats saying the verse as a stand-in for an offering. Seder HaYom treats it as mourning and hope. Soferim and the Rambam both call it a custom, not a law.
Peninei Halakhah, Prayer 23:4,Rambam, Order of Prayer 2:36,Tractate Soferim 18:1,Seder HaYom, Order of Ashrei and Uva LeTzionSunday is nothing like Shabbat. Why call it "the first day of Shabbat"?
The Hebrew is yom rishon bashabbat. In Hebrew, Sunday has no name of its own. It is just "first day," then "second day," and so on up to Shabbat. The Torah numbers the days of Creation this way (Bereishit 1:5 and 1:8). In Vayikra 23:15 the word shabbatot even means weeks: seven shabbatot are the seven weeks counted between Pesach and Shavuot.
Why say it every morning? Peninei Halakhah says the line keeps the mitzvah of remembering Shabbat, from the verse "Remember the Shabbat day" (Shemot 20:8), alive on every weekday. It bases this on the Ramban (Nachmanides, a great medieval Torah commentator from Spain) and on the Ari (Rabbi Yitzchak Luria, the great Kabbalist of Tzfat, who died in 1572).
The Ramban quotes the Mekhilta (an early collection of rabbinic teachings on Shemot). Rabbi Yitzchak says: do not count the way others count. Count for the sake of Shabbat. The Ramban explains that other nations give every day its own name, while Israel counts "first toward Shabbat, second toward Shabbat," so Shabbat is remembered every day. He calls this the plain meaning of the verse. Peninei Halakhah adds that in English, days are usually named after ancient gods.
The Mekhilta also records a second teaching. Rabbi Elazar ben Chananiah says: remember Shabbat from the first day of the week. If you come across something nice, set it aside for Shabbat.
The Gemara shows two ways of living this out. Shammai the Elder (a great sage from about 2,000 years ago) ate every day in honor of Shabbat. If he found a better animal later in the week, he ate the first one and saved the better one. Hillel the Elder had a different trait: everything he did was for the sake of Heaven, as the verse says, "Blessed be Hashem, day by day." The Gemara puts the two schools side by side: Beit Shammai say prepare from the first day of the week, and Beit Hillel say "Blessed be Hashem, day by day." It records both and does not choose.
Bereishit 1:5 and 1:8,Vayikra 23:15,Peninei Halakhah, Prayer 23:4,Peninei Halakhah, Shabbat 1:9,Ramban on Shemot 20:8,Mekhilta DeRabbi Yishmael, Bachodesh 7,Beitzah 16aDid God really "found the earth upon seas"? And which earth is meant?
The first two verses say: the earth and all that fills it belong to Hashem, the inhabited world and all who live in it. For He founded it upon seas and set it firm upon rivers. Two things puzzle readers. Which earth is this, and how can land be built on water?
Rashi (the main Torah commentator, France, 1000s) says "the earth" is the Land of Israel, and "the inhabited world" is the other lands. On the next verse he adds that seven seas and four rivers surround the Land of Israel: the Yarden, the Yarmuk, the Karmiyon and the Puga. Radak reads the first part differently. For him "the earth" is the whole earth, as in the first verse of Bereishit, and "the inhabited world" means the places where people live.
What about built on water? Radak says the earth was not first made the way it is now. It began fully covered by water. Then, in Bereishit 1:9, God says the waters should gather in one place so dry land appears. He did it that way, Radak says, to show that everything is in His hand and He turns nature as He wishes. Ibn Ezra (a Spanish commentator of the 1100s) agrees: by nature the earth was made to lie under the water, and by God's will part of it dried.
Radak also explains the small word al. It usually means "on," but it can mean "next to." In Bamidbar 2:20 the tribe of Menashe camps al, next to, the tribe of Efrayim. On this reading the land was set beside seas and rivers.
So none of these three reads the verse as ground floating on a sea. Rashi has seas around the land. Radak and Ibn Ezra have the land rising out of the water, or standing beside it. The commentators split on which earth the psalm means. The gates in the second half of the psalm are explained with Returning the Torah, when the scroll goes back into the ark and this psalm is said again.
Tehillim 24:1-2,Rashi on Tehillim 24:1-2,Radak on Tehillim 24:1-2,Ibn Ezra on Tehillim 24:1,Bereishit 1:9,Bamidbar 2:20