Parshat Bamidbar marks an important transition in the structure of Kelal Yisrael, in which the Leviim assumed the role hitherto reserved for or at least designated for the bekhorot This change itself raises many issues, as Chazal discuss, calling into question the very purpose of initially infusing the bekhorot with such short-lived kedushah.
The pesukim that describe this development further challenge us to understand both the nature of this transition, as well as the prevailing character of keduashat bekhor. Even as the Torah continually stresses, with the word "li", the total commitment and dedication that Hashem will demand from the Leviim (Bamidbar 3:12,41, 45- "ve-hayu li halviim" etc.), the Torah also characterizes not only the initial, but also the continuing status of the replaced bekhor in the same terms! Thus, we note the triple usage of "li" in the pasuk that concludes Hashem's instructions to Moshe on this matter (Bamidbar 3:13)- "ki li kol bekhor be-yom hakoti kol bekhor be-eretz mizrayim hiqdashti li kol bekhor be-yisrael me-adam ad behemah li yihiyu ani Hashem" (see Bekhorot 5a).
The Torah discusses the mitzvah and status of bekhor differently in various contexts. In parshat Bamidbar, bekhor's special status, which at least partially seemingly persists, is explicitly linked to makat bekhorot, even as the transition to the Leviim is formulated. In parshat Bo (Shemot 13:2), also in the context of the commemoration of yetziat Mizrayim, we are informed that the bekhor is to be sanctified- "kadesh li kol bekhor peter kol rehem be-benei yisrael ba-adam u-babehemah li hu". The Neziv (Haamek Davar, ad. loc.) questions how this act of sanctification is manifest upon a child. [Chazal in other contexts argue that kedushah signifies perishah-separation. See Rambam, Hil. Bekhorot 1:1.] In parshat Korah (Bamidbar 18:15), perhaps linked with the mitzvah of bikurim (18:13) (see Sefer ha-Hinukh ,no. 40, and Moreh Nevukhim), the Torah underscores the need to redeem the bekhor: "akh padoh tifdeh eit bekhor ha-adam...".
While the connection to makat bekhorot dramatizes the distinctive status of bekhor and underscores the need for one manifestation of "ki li hu", that of total dedication to avodat Hashem unambiguously defined, the link to bikurim perhaps implies a more general theme of "ki li hu", according to which the bekhor constitutes an appropriate representative of the broader population of Kelal Yisrael. Moreover, the obligations to sanctify and redeem appear irreconcilable. Indeed, the Rashbam argues that the formulation in parshat Bo reflects only the status of bekhor before the transition, while the pesukim in Korah refer to the contemporary. The Rambam actually omits reference to human bekhorot when he codifies the mitzvah of "kadesh li kol bekhor" in Sefer ha-Mizvot (aseh no. 89), although the actual source in Bo includes both animal and human bekhorot. However, Seforno projects that the themes of kedushah and pidyon are compatible. The standard pidyon ha-ben ceremony includes the pasuk of "kadesh li" immediately after the pasuk of "u-peduyo mi-ben hodesh tifdeh". In fact, the Rambam in Yad ha-Hazakah does include human bekhorot in the mitzvah of "le-hafrish bekhorot", codified in Hil. Bekhorot (1:1), even as he projects the mitzvah of pidyon bekhorot in Hil. Bikurim (11:1).
An examination of the ceremony of pidyon ha-ben reveals other facets of this mitzvah that require clarification. The great joy that is reflected in the ceremony and accompanying formulae convey that this pidyon is perceived not as an unfortunate derogation of status, or loss of spiritual opportunity, but as an authentic expression of spiritual ambition and an affirmation of kedushat Yisrael. Some formulations conclude the berakahah with "mekadesh yisrael le-pidyonam", though this is not our normative practice.
Perhaps the significance of pidyon ha-ben lies precisely in the very fact that the mitzvah of pidyon does not completely negate the initial mitzvat kedushah or render superfluous (or spiritually insignificant) the prior state of perishah. The fact that the principle of "ki li kol bekhor" persists on the basis of "li yihiyu" despite the transition of the avodah to the Leviim may be responsible for the special joy and singular spiritual meaning associated with pidyon ha-ben. Notwithstanding the subsequent exclusion of bekhorot from the actual avodah, this perspective effectively conveys the ideal that the opportunity to serve in that elite capacity was initially and in some (abstract) respects still remains the potential legacy of every single family of Kelal Yisrael. Furthermore, it accents that shevet Levi continues to serve as the representatives of that original integrated population. Moreover, a joyous pidyon that reflects and affirms initial kedushah even in absence of the actual potential to serve and which anticipates a spiritually rich life of torah and yirat shamayim as conveyed in the accompanying formula ("ve-yikanes zeh ha-ben le-hayyim, le-torah u-leyirat shamayim...she-kesheim she-nikhnas le-pidyon ken yikaness le-torah u-le-hupah, u-le-maasim tovim"), not despite but because of the pidyon, is one that truly reflects a profound theme of kedushat yisrael. It powerfully projects that "ki li kol bekhor" and all that it implies, transcends the avodah and can be channeled, manifested and expressed in ways that are also accessible to all members of kelal yisrael. In this way, the otherwise distinct themes of makat bekhorot and bikurim, of Hil. Bekhorot (kedushah-avodah) and Hil. Bikurim (reishit-pidyon) converge bearing the singular message of "ki li kol bekhor be-yom hakoti kol bekhor be-eretz mizrayim hiqdashti li kol bekhor be-yisrael me-adam ad beheimah li yihiyu Ani Hashem".