וּרְדַפְתֶּ֖ם אֶת־אֹיְבֵיכֶ֑ם וְנָפְל֥וּ לִפְנֵיכֶ֖ם לֶחָֽרֶב
I ścigać będziecie wrogów waszych i padną przed wami od miecza.
Radak
Thou didst take Thy seat in the throne: – Thou satest on the throne of judgment, Thou who art A judge of righteousness, – to exact Thy judgment from him who reviled the armies of the living God. The lamedh of לכסא is used in the place of beth. And so also lamedh is used in the phrase לחרב לפניכם, “(they shall fall) before you by the sword” (Lev. 26:7), where לחרב is equivalent to בחרב; (and again in the verse) “I have slain (a man) by my wounding” (לפצעי, Gen. 4:23).
Ramban
AND YOUR ENEMIES SHALL FALL BEFORE YOU BY THE SWORD. He assured them at first that they would chase their enemies and that they would fall by their sword,25See Verse 7. and then He stated again by way of repetition [in the verse before us], and your enemies shall fall before you by the sword, in order to give them fortitude of heart and strength so that five [of them would not be afraid] to pursue a hundred. He [furthermore promised that He] would put faintness into the heart of their enemies, so that a hundred would [in fact] flee before five, and would all fall by the sword of the five, for it would be possible that they [a hundred people] would flee because of the sword and because of their fear, but that they would not be able to kill them by the sword because of their few numbers [therefore He mentioned specifically that they would be able to put them to the sword too]. Rabbi Abraham ibn Ezra has said that this repetition [in our verse] means that they [the enemies] will fall continually, time after time, without regaining [their strength].