The Tribe of Levi was consecrated to service in the Mishkan in place of the first-born (Bemidbar 8).
Then the Torah tells us (Bemidbar 8,16)
טז כִי נְתֻנִים נְתֻנִים הֵמָה לִי, מִתּוֹךְ בְּנֵי יִשְּרָאֵל: תַּחַת פִטְּרַת כָל -רֶׁחֶׁם בְּכוֹר כֹּל, מִבְּנֵי יִ שְּרָאֵל--לָקַחְּתִּי אֹּתָם, לִי.
16 For they are wholly given unto Me from among the children of Israel; instead of all that open the womb, even the first-born of all the children of Israel, have I taken them unto Me.
What is the meaning of the doubly-mentioned nesunum-nesunim (given)? Plus, this same doubly-mentioned nesunum-nesunim occurs earlier (Bemidbar 3,9).
Rashi says the first giving is for the carrying of the Mishkan components; the second giving for the service of singing during the Avodah in the Mishkan.
Ibn Ezra writes that this implies a two separate “givings” of the Leviim. The first refers to the giving of Leviim to those Kohanim alive at that time in the desert; the second refers to their descendants of the Kohanim who will take their place.
Alternatively, Ibn Ezra suggest the doubled “giving” is to reinforce the action of the giving of the Leviim.
Medrash Lekach Tov explains that one giving is for the service in the Mishkan; second giving for the Bais haMikdash.
Malbim mentions that it is impossible to acquire something that is not in the world yet. Therefore, the doubled mentioned giving is as if to say that in each generation the Jews would give the Leviim to be their agents on their behalf.
Sfrono explanation is in keeping with the accepted idea that a repeated verb comes to emphasize its impact. “They are certainly given to him – that all of their service shall be according to the word of Aharon and his sons and to no one else.
Alternatively, Sforno suggests that the first “giving” is the voluntary giving of the Leviim to His service beginning with the response to Moshe at the Golden Calf. The second giving is that of the Jewish nature to give Maaser to the Leviim who no longer received land apportionments leaving them with no means of income.
Ohr haChaim states “the verse doubled the word “given” with the intent to obligate the recipient to accept the gift and then he cannot say, ‘I do not want to accept this gift’. Even though a person can refuse to accept a gift because as long as it has not come into one’s hand, one can refuse to acquire it.”
Why would Aharon not want to accept the gift that it would be necessary to coerce Aharon to accept the gift of the service of the Leviim?
Ohr haChaim states, “the reason to refuse this gift is that the Kohanim would now be prohibited from performing the service assigned now to the Leviim; and if any future Kohen would be liable for the death penalty if they did this service.”
Perhaps we can also suggest another explanation. There is a halachic concept not to accept gifts so as not to make one feel dependent on others. Thus, Aharon might have a legitimate reason to refuse such a gift from the Jewish people. However, HaShem emphasizes that the doubled gifting that despite the first giving from the Jews, there is a second giving from HaShem. This giving is an expression of the Divine Will and not in the material nature of gifts.
