The divine instruction given to the Israelites for this specific military campaign is entirely unique. They are told to march directly to the battlefield, yet they must avoid engaging in combat altogether. Going to the front lines the next day is not meant for actual fighting [מלבי״ם]. Instead, this strategy serves as a direct response to the people's earlier plea, where they reminded God that He was the one who originally gave them their land. God acknowledges that their claim is just, and therefore, it is His responsibility to secure their inheritance and fight on their behalf [רש״י].
As the Israelites prepare to face their opponents, they are given a twofold command regarding how to hold their ground. Some explain that this dual instruction serves to urge the people forward quickly while strictly warning them not to provoke the enemy [מצודת דוד]. Others view this as a gradual process: first, the Israelites must take their positions projecting strength and power, but immediately afterward, they are simply to stand in place. No ongoing physical effort is required of them, only a passive, steady stance [מלבי״ם].
The plan requires the people to march out and face their enemies while doing absolutely nothing, relying entirely on the fact that God is with them and will single-handedly decide the outcome of the war [מלבי״ם]. Trusting completely in this divine promise, the people believed God's words, moved with urgency, and rose early the very next morning to carry out their instructions [רש״י].