Seforno: It incorporates the four Chalos that are separated fom the Lachmei Todah, the Sh'tei ha'Lechem on Shavu'os and Chalah.

Rashi: Because the Parshah of Matnos Kehunah is dear to Hashem, He begins it with a K'lal and ends it with a K'lal, placing the P'rat (the details) in the middle.

Seforno: "Kol T'rumos ha'Kodashim" actually comes to include what the owner separates from the Lachmei Todah, ¹ the Sh'tei ha'Lechem and Chalah.

Rashi #1: Hashem made a covenant with Aharon, on something that is healthy and that lasts, and that makes other food 'healthy'.

Rashi #2: It teaches us that, like the covenant that Hashem made with salt - that it never goes bad - the covenant that Hashem made with the Kohanim will never ?go bad?.

Rashi #3 (on Chulin, 133b) and Targum Yonasan: It teaches us that, like the covenant with salt, the covenant with Aharon will never cease. ¹

R. Bachye #1: It means ?a covenant that is firm - that will not be destroyed - a location where there is salt is destroyed, and is uninhabitable. ²

R. Bachye (according to Kabalah): A covenant that preserves the Kohanim, just as salt preserves the meat. Now salt is formed by water (Midas Rachamim) that is affected by the heat of the sun (Midas ha?Din). So too, does the B?ris incorporate the continuity of the world and its destruction. ³

Rashbam: It means - metaphorically - that it is a covenant that lasts for all generations. ⁴