Why does the Torah repeat this Pasuk, which was already said in Shemos (29:38)?
Rashi: The Pasuk in Tetzaveh was said exclusively with regard to the Shiv'as Yemei ha'Milu'im, 1 whereas the current Pasuk applies to future generations.
Ramban: It repeats it here in order to incorporate all the Korbanos in one location together with those that it has not previously mentioned. 2
Why does the Torah rite "Keves Echad and not 'Keves ha'Echad' (as it said in Shemos, 29:38)?
Ramban (on Pasuk 2 and R. Bachye): To teach the Kohanim to ring the Nesachim in the Name of Hashem Echad 1 and not for any other motive.
As if the Torah had written 'Es ha'Keves shel Echad'. Moreover, "Echad", whose Gematriyah is thirteen, also hints at the number of Kohanim who participated in the Korban Tamid (R. Bachye).
Why is it necessary to bring two Korb'nos Tamid daily? Why will one not suffice?