The victory in Christ is our faith that has overcometh the world

"Finally, the impotence of all human strength in the spiritual conflict is briefly demonstrated by John when he says, 'Whosoever is born of God cannot sin; for his seed remaineth in him' and in another place he adds the reason, that 'this is the victory that overcometh the world, even our faith.'" - John Calvin, the Institutes, 2. 5. 11.