Each day of the week, the Levi’im sang a different song that corresponded to what took place during the six days of Creation (Tamid 7,4). Following in their footsteps, every day we say the song that corresponds to that particular day. On Shabbos we recite the mishna which mentions all of the songs for the entire week (Magen Avraham 132,4).
“Hashem is the earth and its fullness, the inhabited land and those who dwell in it” (Tehillim 24). On the first day of Creation, the earth was created and Hashem was established as the Owner of everything, and on Sunday we start the week off with this song (Rosh Hashana 31a). Keeping this in mind helps us start off the week with the recognition that everything belongs to Hashem.
On the fourth day of the week Hashem created the sun, moon and stars. Although these luminaries were created to give light to the world, some people are drawn to deify them. In the future, G-d will punish those who worship them (ibid.), and for that reason on the fourth day we sing, “G-d of vengeance, Hashem” (Tehillim 94).
Text Copyright © 2011 by Rabbi Daniel Travis and Torah.org