Rashi on Numbers 18:19/רש"י על במדבר י״ח:י״ט

1כל תרומת הקדשים ALL THE HEAVE OFFERINGS OF THE HOLY THINGS [… HAVE I GIVEN THEE] — Out of a feeling of affection for the contents of this section, Scripture comprehends it at first in a general statement (v. 11: וזה לכם תרומת וגו׳), and comprehends it also in a general statement at the end (in this verse) and enumerates the details in between (vv. 12—18) (Sifrei Bamidbar 118).

2ברית מלח עולם [IT IS] A COVENANT OF SALT FOR EVER — This means that He made a covenant with Aaron by means of something which is wholesome and lasting and keeps other things wholesome (Sifrei Bamidbar 118).

3ברית מלח A COVENANT OF SALT — Another explanation is that ברית מלח is equivalent to כברית מלח, and the meaning is: like the covenant that was made with salt that it will never decay.