The Ark of the Covenant represents the Divine presence among the Israelites. Having firmly established his rule, David seeks to bring the Ark to a permanent, honorable resting place near his own home [ביאור שטיינזלץ]. He gathers the nation and travels to Baale Judah. The primary approach among commentators is that this is another name for Kiriath-jearim, a city situated on a plain within the territory of the tribe of Judah [רש״י, מצודת ציון, רד״ק, מלבי״ם, אברבנאל]. Others suggest that this name refers to the honored leaders of Judah who joined the expedition [ביאור שטיינזלץ], or to the local residents who marched alongside David to escort the Ark out of their city [אברבנאל]. Ultimately, the people gathered and traveled to this specific location with the unified goal of retrieving the Ark [מצודת דוד, רד״ק, אברבנאל].
According to ancient tradition, there were actually two arks during this period: one holding the unbroken tablets of the law, and another containing the shattered remains of the first tablets. David's specific mission is to retrieve the primary Ark containing the whole tablets, which was topped by the Cherubim [אלשיך]. This Ark is deeply associated with the Name of God, specifically the title "Lord of Hosts," which highlights His direct and active involvement in the physical world [אהבת יהונתן]. The double emphasis on God's Name associated with the Ark is understood in several ways. The simplest explanation is that it serves as a direct introduction, stating that the Ark is known by a specific title, which is then immediately revealed as the God of Hosts who sits upon the Cherubim [רש״י, מצודת דוד]. Alternatively, this dual mention corresponds to the two arks, noting that the Ark with the whole tablets bore God's explicit Name, while the other carried only a lesser title [אהבת יהונתן]. Another perspective suggests that God's Name was publicly proclaimed and sanctified twice through the miracles associated with the Ark: first when it was captured and held in the fields of the Philistines, and again when it resided among the Israelites [אברבנאל, רד״ק].
The profound holiness of the Ark, serving as a chariot for the Divine presence, explains why David insists on leading the entire nation rather than merely sending a delegation [מלבי״ם]. However, this elevated spiritual status also sets the stage for the tragedy that soon follows with the sudden death of Uzzah. In their overwhelming enthusiasm to transport the Ark, the people make a critical error in how it is moved. Because the Ark represents the heavenly chariot, it requires transportation in a state of absolute reverence, carried specifically upon the shoulders of the Levites who parallel the heavenly bearers. Placing it on a cattle cart instead is a fundamental mistake that directly leads to disaster [מלבי״ם, אלשיך].