The ruler of this world was cast out by the cross. His head was crushed by the cross. He fell from heaven and has been destroyed—past tense. He had the power of death and would be destroyed when Jesus died on the cross and when Jesus rose again, and I sent it to him.
So, we need to live like that’s true. We need to be victorious people as part of what living is—soldiers of Christ.
But we also remember that the Devil still prowls around like a roaring lion. He still seeks someone to devour according to Peter (1 Peter 5). We have to resist him. Resist! But there is a promise: the suffering will end when the God of all grace will himself restore, confirm, strengthen, establish his church.
But the devil is still active. That’s the context of the armour of God in Ephesians 6, the context of the parable of the weed in Matthew 13. The weeds have not yet been gathered up. Satan and his works will be finally removed at the final judgment. But as things stand, the weeds grow amongst the wheat.
In the meantime, there are references to Psalm 110 throughout the New Testament that the Lord Jesus is destroying—in the present tense—every rule, every authority, and every power. Our Lord Jesus is reigning, but he’s reigning with work that is still ongoing, putting all his enemies under his feet. The last enemy to be destroyed is death—that’s what the devil brought about. People still die.