A true leader often stands apart by where he finds his power. While ordinary rulers pride themselves on their personal might and independence, this ideal king draws his deep joy and strength from a total dependence on God. The exact identity of this leader is open to interpretation. Some view him as King David himself, while others understand him to be the future Messiah [רש״י, מצודת דוד].
The primary approach among commentators is that this strength refers to the physical power and bravery that God grants the king [רד״ק, אבן עזרא, מצודת דוד, ביאור שטיינזלץ]. However, this strength can also be understood in a broader spiritual sense. It may represent the guiding power of the Torah that leads the king toward truth, or even the ability to accept suffering with the peaceful realization that all of God's actions are for the ultimate good [חומת אנך].
Typically, a human ruler is reluctant to rely on the power of another king or be saved by him, because doing so highlights his own weakness. In contrast, this king is deeply proud and happy to lean entirely on the power of God [מלבי״ם]. This happiness is so profound that it remains steady even when the king has not yet reached a state of complete peace [ביאור שטיינזלץ]. On a deeper level, the king's immense joy in his salvation goes far beyond his personal rescue. His true happiness stems from the redemption of the Divine Presence and its release from exile [אלשיך, חומת אנך].
The relationship between the king's joy in God's strength and his rejoicing in God's salvation is viewed in different ways. Some see the dual expressions of happiness as a poetic repetition, conveying the same thought in different forms [מצודת דוד]. Others find a fundamental difference between the two emotional states. The first type of joy represents a constant, permanent state of mind, which is naturally connected to God's ongoing strength. The second describes a sudden, overwhelming burst of emotion triggered by a new occurrence, perfectly matching the experience of a specific, fresh act of salvation [מלבי״ם]. The sheer magnitude of this happiness is emphasized by a double expression of intensity, capturing an enormous overflow of enthusiasm and delight [מאירי].