Why does the Torah repeat "b'Yom ha'Shabbos"?
Rashi (in Pesachim, 58a): On Shabbos the Kohanim replaced the old loaves with the new ones, and burned the bowls of frankincense.
What are the connotations of "Tamid" in this Pasuk?
Rashi (in Chagigah, 26b): "Tamid" in this Pasuk 1 means day and night, since the loaves remained on the Shulchan from Shabbos to Shabbos. When replacing the loaves, two Kohanim place the new loaves as the old ones are being removed (Chachamim, Menachos 99b).
R. Yosi (Menachos 99b): As long as the Shulchan does not spend a night without bread, this is 'Tamid'.