Following moments of crisis and rejection, the reality shifts entirely to one of security. The righteous sit safely while their enemies fall [אבן עזרא]. This state of peace, which also points toward a future redemption [רש״י], is filled with sounds of joy and salvation echoing from within the tents of the righteous. The primary approach among commentators is that this noise is the sound of the righteous praising God, singing before Him, and loudly declaring His salvation.
A distinct historical and miraculous layer is connected to this joyous singing, specifically the downfall of the Assyrian army during the days of King Hezekiah. A wondrous parallel unfolded during this event. While the Israelites sat safely inside their homes singing songs of praise for the Passover holiday, God acted outside to strike down the enemy camp. The joy belonged to the people singing inside, while the salvation was carried out by God outside. As the songs of gratitude grew louder from within the tents, the miraculous salvation intensified on the battlefield [אלשיך, מלבי״ם].
The content of this song of gratitude focuses on God's strong hand acting with power, courage, and wealth [רש״י, מצודת דוד, ביאור שטיינזלץ, מצודת ציון, רד״ק]. Through this declaration, the righteous openly acknowledge that their victory does not come from human effort, but entirely from God alone [אלשיך, מאירי]. Furthermore, this display of divine strength describes an unfolding military process. At the beginning of the song, God is described as gathering His forces and preparing for battle. As the singing continues, it reflects the moment God fully exerts His strength and completely defeats the enemy camp [מלבי״ם].