Parashas Eikev · Passuk 10:8
At that time GOD set apart the tribe of Levi to carry the Ark of GOD’s Covenant, to stand in attendance upon GOD, and to bless in God’s name, as is still the case.
Torah Temimah points to Zevachim 16a.
TT lemma: לעמד לפני ה' (unit 2 of 2).
English: “To stand before Hashem”: Every sacrifice whose blood was received while sitting is invalid, but on a bamah it is valid, as it is written, “to stand before Hashem to serve Him” — before Hashem, and not on a bamah.
Custom (standing for avodah; bamah exception)
Receiving blood must be done standing in the Temple; bamot lack the “before Hashem” requirement of posture.