VA'HA'SI'AYNU HSHEM ET BIRKAT MOADECHA
I’ve been bothered by English translations of the phrase והשיאנו...את ברכת מועדיך.:
Birnbaum, Sacks, and ArtScroll all translate it as Bestow upon us…the blessings of your holidays or something to that effect.
The problem is that the first word - va’ha’si’aynu - is a self-contained clause, which means “Elevate us”. To view את as an object-marker, therefore, makes no sense.
I suggest that et in this context means “with” or “by means of” - as in the clause ויהי ה' את יוסף [The Lord was with Yosef – Bereshit 39:2]* We are thus requesting that the material blessings of the holiday have the effect of elevating us and refining us.
The petition Va'ha'si'aynu, therefore, is analogous to the petition, קדשינו במצוותיך – which I see as a petition that the mitzvot have the effect of sanctifying us.
*(For another example of et meaning “together with,” please refer to my essay on Aliya L’regel.