Shared ground
This passage presents Israel’s advance as a commanded, boundary-crossing move: they are to cross the Arnon valley and shift from traveling to taking territory. It also frames the coming conflict as focused on a specific ruler—Sihon, king of Heshbon—rather than a vague idea of conquest.
The text makes two claims side by side: (1) Sihon and his land are already “given” into Israel’s hand, and (2) Israel must “begin” to possess the land by contending with him in battle (begin). In other words, the outcome is spoken of as decided, while the means still includes real confrontation.
A second theme is reputation and regional impact. “This day” marks the start of a fear effect among other peoples who hear reports about Israel. The passage expects the news of Israel’s movement and victories to travel and to produce dread, trembling, and anguish beyond the immediate battlefield.
Where interpretation differs
How to understand “I have given…Sihon…and his land.” Some read “given into your hand” as emphasizing certainty of outcome (God’s decision), while still allowing for a process that unfolds through warfare. Others hear it as stronger language of transfer or control already granted, so the fighting is mainly the enactment of what is already handed over.
How wide “peoples under the whole sky” is meant to be. Some take it as broad but still regional—an ancient way of saying “everybody around here.” Others treat it as intentionally universal language that portrays Israel’s God as able to affect perceptions far beyond the local area.
How exact “this day” is. Some read it as the literal day of this command; others take it as “from this point forward,” marking a new phase rather than a 24-hour window.
Why the disagreement exists
The key phrases are naturally expansive and time-marked (“given,” “under the whole sky,” “this day”), but they are not defined with modern precision. The immediate setting is a concrete border crossing and a named king, while the explanatory line about fear reaches beyond the immediate scene. That mix invites different judgments about how literal or rhetorical the scope and timing are.
What this passage clearly contributes
Explicitly, it connects divine gift-language (“given into your hand”) with human action-language (“begin to possess…contend in battle”). It also portrays the conquest as having a public dimension: Israel’s movement and victories are expected to generate widespread fear once reports circulate. The text therefore links geography (crossing Arnon), politics (a city-king and his land), warfare (contending), and perception (dread among other peoples) into one coordinated moment in the narrative.