69 The words “their territory extended” are supplied in the translation for stylistic reasons. In the Hebrew text vv. 47–49 are all one sentence, but for the sake of English style and readability the translation divides the text into two sentences.
70 Mount Siyon (the Hebrew name is שִׂיאֹן [si’on], not to be confused with Zion [צִיּוֹן, tsiyyon]) is another name for Mount Hermon, also called Sirion and Senir (cf. Deut 3:9).

In other versions

from Aroer, which is on the edge of the Valley of the Arnon, as far as Mount Sirion (that is, Hermon),

This land extended from Aroer on the rim of the Arnon Gorge to Mount Sirion (that is, Hermon),

from Aroer on the rim of the Arnon Valley as far as Mount Sion (that is, Hermon)

So Israel conquered the entire area from Aroer at the edge of the Arnon Gorge all the way to Mount Sirion, also called Mount Hermon.

from Aroer, which is on the bank of the wadi of Arnon and as far as Mount Sirion; that is, Hermon,

From Aroer, which is by the bank of the river Arnon, even unto mount Sion, which is Hermon,

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