Revelation 12:10-11

10Then I heard a loud voice in heaven that said: ‘Now God has saved his people from Satan's power! God has shown his great power as King. His Messiah has authority to rule. Satan said bad things against our people. He never stopped telling our God that our brothers and sisters are guilty. But now God has thrown him out of heaven.

11Our brothers and sisters fought against him and they won. They could do this because of the death of the Lamb as a sacrifice. They continued to speak God's true message. They were also ready to die as God's servants. That is why they were able to win against Satan.