ואת ישראל בבני בכר כל תחת ‘ה אני לי הלוים את ולקחת" (מא ג) "ישראל בני בבהמת בכור כל תחת הלוים בהמת
In the kinnah of "Eilai Tzion V’areha", said in the communities of Ashkenaz on Tishah B’Av, we lament: "Ali zivchi temidecha upidyonei bechorecha." Many have asked: Doesn’t this lamentation mention things that were nullified because of the Churban? Why is the mitzvah of pidyon haben mentioned here if it is still practiced in our time?
Harav Yitzchak Zev Soloveichik of Brisk explained: The kavanah of the lamenter is not the nullification of the mitzvah of pidyon haben, but rather the loss of the avodas haLevi’im, which are referred to by him as "pidyonei bechorecha," as explained in this parashah that the holiness of the firstborns was redeemed and transferred to the Levi’im.
Toras Zev p. 82
