By the Blood
In chapter 12 of Revelation we see depicted Satan's war on the people of God. He rages against the church, working hard to destroy it, but in verse 11 we read, "They [the children of God] overcame him by the blood of the Lamb."
This is a fascinating moment. Revelation depicts much death and destruction, much "tribulation," as the enemy thrashes about in his rage and jealousy, but the children of God win the victory not by might, not by brilliant strategizing, not by charismatic leadership, but "by the blood of the Lamb."
D. A. Carson says this:
The preposition translated as by in the NIV should be rendered "on the ground of." When all his [Satan's] accusations are brought before us--so many of them entirely justified, if we gauge things only by the quality of our faithfulness--Satan is silenced when we insist that our acceptance before God is grounded not in ourselves but in the death of Jesus Christ. "Who is he that condemns?" Paul exultantly asks. "Christ Jesus, who died--more than that, who was raised to life--is at the right hand of God and is also interceding for us" (Rom. 8:34). We neither have nor need another ground for our acquittal.As Martin Luther wrote, "All other ground is sinking sand."