The second half of parshas Korach (chapter 18 ff.) outlines the responsibilities of the Kohanim to guard and preserve the sanctity of mishkan. In this task they are to be assisted by the Leviyim. After this outline of responsibilities, the Torah lists the various gifts to be given to the Kohanim, the twenty-four matenos kehuna, followed by the gift given to the Leviyim, namely ma'aser - a tenth of the agricultural produce - and the obligation of the Levi to give a portion of his ma'aser to the kohein, terumas ma'aser. At first glance, all of these "gifts" granted to the Kohanim and the Leviyim, although generally referred to as matanos, are not gifts conceptually but actually are a form of remuneration for their service in the mikdash. This is seemingly verified by the verse concerning ma'aser, "ki sachar hu lachem cheilef avodaschem b'oheil mo'ed - for it is a wage for you in exchange for your service in the Tent of Meeting" (Bamidbar 18:31, see also 18:21).[1]
However, the fact this verse appears only with respect to the ma'aser gift for the Levi and not with respect to any of the gifts given to the Kohanim leads several of the commentaries to note a fundamental difference between the nature of the gifts to the Kohanim and that given to his Levi counterpart. Ohr HaChayim, on the verse "ani chelkecha v'nachaloscho b'toch Bnei Yisroel (18:20), states concerning the matenos kehuna, "there is no item which Israel produces [in which] HaKadosh Baruch Hu does not have a share along with them, but the Kohein takes it [in His stead], with regard to fruits, bread, meat, wine, oil, and all the other twenty-four gifts." This clearly indicates that the gifts are really due to Hashem, and He grants them to the Kohanim. However, concerning ma'aser, Ohr HaChayim writes clearly, "Concerning the Leviyim, He did not state 'ani chelkecha' etc. for the leviyim do not acquire the share of G_d. This is why they too have to give the share of G_d, namely teruma - ma'aser from the ma'aser. This is like common salary to serve the holy one, the kohein, and [in] the Ohel Mo'eid." Later (v. 31), Ohr HaChayim utilizes this distinction to explain why teruma has sanctity and restrictions concerning its eating whereas ma'aser has no such restrictions. In contrast to the priestly gifts which are granted from Hashem's share, kiv'yachol, ma'aser is characterized as unsanctified salary for the Levite's work.
Netziv, in his Ha'ameik Davar (18:31), corroborates Ohr HaChayim's thesis and writes concerning ma'aser: "And you shall eat it in all places É even the portion to be eaten which one might have thought É is given for their service and, as a result, one should treat it with a degree of sanctity; therefore, the verse clarifies that it may be eaten even in a cemetery, 'for it is a wage for youÉ', not like the matenos kehunah, which come as a present from cheilek gavo'a (G_d's portion), rather it is characterized as salary, and, as such, has no sanctity." Netziv with the use of the phrase, "cheilek gavo'a", alludes to several places in the Talmud where the Kohanim are considered as eating from the shulchan gavo'a, the table of the One on High (see Beitza 21a, Kiddushin 52b, and others). Netziv apparently extends this Talmudic concept to kadshei gevul, gifts granted the Kohein even outside the midkash, such as teruma, and perhaps even to those without specific sanctity such as reishis hagez (first wool harvest) and zero'a, lechayayim, and keiva given from each animal slaughtered outside the mikdash.[2]
What emerges from the above duality is that there are two forms of gifts granted by Hashem to the Kohanim and Leviyim; the first type represents eating at the King's table, so to speak, and the second gift is a form of wages for service to be utilized by the public servant. Perhaps these two models can serve as the basis to homiletically derive dual messages for the relationship of Hashem Yisborach to each individual Jew. Certainly every Jew can partake of a korban shelamim or other kadashim kalim, the meat of which is characterized once again as from shulchan Gavo'a (see Beitza 21a). Even ordinary Yisraelim partake of agricultural produce which are imbued with sanctity: ma'aser sheini - the second tithe to be eaten in Jerusalem in a state of tahara - and neta riv'ai - the produce of a tree's fourth year's fruit yield. The Talmud (see Kiddushin 52b, 54b) debates whether these are considered mamon hedyot or mamon gavo'a. Perhaps the latter view (the accepted view of Rabbi Meir) contains an element in common with teruma, namely some aspect of even the ordinary Jew receiving sustenance from Hashem's table. Whereas most bounty one partakes of in this world is not imbued with sanctity, all of our physical blessings, in a sense, come from our Creator's "expense account" which he is granting us to utilize for his service. In the famous words of Rambam (Peirush Hamishnayos, Sanhedrin 10:1 based on Avos 4:2, also see Hilchos Teshuva 9) explains that the meaning of Chazal's statement, "s'char mitzvah mitzvah", is that the purposely of physical "reward" is this world is more physical blessings with which to perform additional mitzvos. An analogy can be drawn to a successful salesman, who utilizes his initial budget to great success for his company. His employer is most likely to grant him a large budget for his next trips in order to net an even greater profit for the company. So too when Hashem sees that we are utilizing His blessings properly, He will often grant us more to do even more. This follows the "ma'aser model", one of salary.
But, at its core, we are all beneficiaries of the "King's table", as represented by the teruma model. Iyov (35:7) teaches "im tzodakto ma titein lo - if you are righteous, what do you give Him?" Ultimately, all that we do does not affect Hashem at all, and, ultimately, the eternity that we gain is for ourselves. Hashem's blessings to us are never really "earned" in the classic sense. In Ramchal's (see Derech Hashem) famous explanation of the purpose of mitzvos, he explains that Hashem grants us eternal reward in a more perfect way such that we "earn" it in order to be spared the embarrassment of "a handout". Bu this is only on the surface level. Ultimately, King David declares, "mimcho hakol u'miyadcha no'sa'nu loch", (Divrei Hayamim I:29:14) - all comes from our Creator, and it is from His bounty and utilizing all the tools He granted us that we serve Him. The verse states "mi hakdimeini vo'ashalem - who has preceded Me and I shall pay him!" (Iyov 41:3). On this, the Midrash (Tanchuma Emor 7) comments that if a person is feeling that G_d's "owes him" because he wears tzitzis, Hashem reminds him that he provided him with the clothing. If one feels he gives massive amounts to charity, G_d reminds him that he provided him with all of the funds.[3] Even our intellect and our very ability to act in the world are all Divinely granted and sustained. Even if, for the most part, it appears that Divine blessings are granted to us in a "ma'aser" style "salary" fashion, fundamentally, we are all like Kohanim partaking of the King's table throughout our lives. May we always merit Hashem's blessings, and, even more importantly, recognizing our King and Father's kindness always.
[1]Indeed, Ketzos HaChoshen (243:43.) seems to apply the halachic category of sechirus po'alim to teruma. But see Miluas Even there that this might be a borrowed use of this terminology.
[2]Postscript: For a more thorough treatment of the distinction between matnos kehuna and matnos leviyah including many sources from Rishonim and Acharonim that do not distinguish between them, see Minchas Asher al Hatorah (Bemidbar 37).
[3]Also see Bemidbar Rabba (14:2) for a different interpretation of this verse which further verifies the Rambam's approach mentioned earlier.