Encamped along the hills of light, Ye Christian soldiers rise,
And press the battle ere the night, Shall veil the glowing skies.
Against the foe in vales below Let all our strength be hurled;
Faith is the victory, we know, That overcomes the world.

This first verse harks back to several battles in the Old Testament where Israel, through faith in God, conquered many foes greater in number and better equipped than they. But the symbolism goes further. The word for “world” is the Greek word kosmos, implying, in context, the world system of thought arrayed in opposition to God. “We know that we are of God, and the whole world [i.e., kosmos] lieth in wickedness” (1 John 5:19).
Strangely enough, Scripture here does not say that through faith we will overcome and gain the victory. Rather, it explains that faith itself is the victory. Evidently, with victorious faith, the overcoming is automatic.
“Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world” (1 John 4:4). (from Days of Praise, Institute for Creation Research)