Others say: On the day of Hakhel (viz. Ibid. 21:12) only mishneh Torah (Devarim) is to be read (and it is to this Hakhel reading that our verse is alluding.)
"on a scroll": and not on a tablet and not on paper, but only on a megillah (a scroll).
"before the Cohanim, the Levites": from the scroll in the azarah (the Temple court).
(Devarim 17:19) "And it shall be with him": From here they ruled: When the king goes out to war, it is with him. When he presides in judgment, it is by him. When he sits down, it is beside him.