תהלים, פרק י״ח, פסוק מ׳

King David recognizes that his military triumphs and his ability to endure the brutal realities of the battlefield do not come from his own personal power. Instead, they are the direct result of divine assistance. God is the one who grants him the necessary physical resilience, while simultaneously working to defeat those who attack him. God strengthens David's limbs, giving him the physical endurance required to withstand the heavy toll and intense effort of military campaigns [אבן עזרא, רד״ק, ביאור שטיינזלץ]. Unlike earlier descriptions of general strength, this endurance is uniquely tailored for the demands of war [מלבי״ם]. The sages note a dual nature to this divine preparation. God not only armed and readied David for combat, but He also spiritually refined and purified him [תורה תמימה].

When facing his attackers, a distinction is made regarding those who actively rise up to wage war against him, as opposed to enemies who simply harbor hatred but take no action [מלבי״ם, אלשיך]. Because God already equipped David with such physical might, David is confident that God will naturally bring these active attackers to their knees [אלשיך]. Their defeat is total. They are brought down to their knees, completely losing their ability to walk or continue the fight [מצודת ציון, מאירי]. The nature of this defeat is understood in two ways. While David stands firm and steady on his feet, his enemies stumble and fall directly beneath him [רד״ק]. Alternatively, the defeat is seen as a divine substitution, where God steps into David's place, fighting the battle and subduing the enemy for him [מלבי״ם].