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 Horayot 13a.
TT lemma: את שבט הלוי (unit 1 of 2).
English: It was taught: Whoever is more sanctified than his fellow takes precedence over him; a Levi precedes a Yisrael, as it is said, “At that time Hashem set apart the tribe of Levi to carry the ark of the covenant of Hashem.”
Custom (order of precedence — Levi before Yisrael)
Levi’s separation for the ark grounds his priority in hierarchical honor within holiness.