What does Luke 11:26 mean?

Jesus finishes His discussion about the relationship between Himself and Satan. Jesus does not work for Satan (Luke 11:14–20). Jesus will conquer Satan and any who belong to him (Luke 11:21–23). Now, Jesus shows that there is no neutral zone. The parable of the restless spirit began with a man who is recently rescued from demonic oppression. He makes the most of his freedom by putting his life and his mind in order. He is as peaceful and well as any human can make himself.

He doesn't realize that this human peace makes him more vulnerable to attack. The demon returns with seven others to possess him, their grip on him stronger than ever. His good place in human society is destroyed.

Jesus explains that those who try not to choose a side by default leave themselves vulnerable to Satan. Satan is the ruler of this world (John 14:30) and all people are born as his "spoil" (Luke 11:22). This is why Jesus has been sending His disciples out to declare the kingdom of God (Luke 9:1–6; 10:1–11). We must intentionally choose Jesus to really be free and live in legitimate peace.

It's tempting to read too much into this parable. Scripture is not saying that someone who has received freedom from sin and oppression and who does not follow Jesus will inevitably be demonized again, or that they are destined for hell. This does parallel passages on apostates: those who have "tasted the goodness of the word of God and the powers of the age to come, and then have fallen away" (Hebrews 6:5–6). But God is more powerful than Satan and all his demons. The man in the parable is not condemned unless he dies having never asked Jesus for rescue from Satan and his sins. Until then, repentance is always an option (1 John 1:9).