The whole of Christ's ministry involved the binding of the demonic realm. The Greek word deo (bound) refers to restrain and curtailment in Scripture.
Satan had to be dominated, overcome and then restricted in order that the darkened nations could be enlightened and consequently liberated.
He had to be put on a spiritual chain (bound). Satan is a prisoner on a chain. Demons are prisoners in chains. Christ not only has authority over them, but he has also given us His people authority over them.
Jesus said just prior to His death in Matthew 12:28-29, “if I cast out devils by the Spirit of God, then the kingdom of God is come unto you … how can one enter into a strong man's house, and spoil his goods, except he first bind (or deo) the strong man? and then he will spoil his house.”
Before we go any further let us establish 1st that this is referring to His earthly ministry.
Secondly, when it talks about Satan and his kingdom being bound, being in chains or being imprisoned it is not talking about physical metal chains a physical brick prison because Satan is not a physical being. He is a spiritual being. It is talking about a spiritual condition of restraint that curtails him in regard to his influence and power.
Mark 3:11, 23-27 also records: “unclean spirits, when they saw him, fell down before him, and cried, saying, Thou art the Son of God ... And the scribes which came down from Jerusalem said, He hath Beelzebub, and by the prince of the devils casteth he out devils. And he called them unto him, and said unto them in parables, How can Satan cast out Satan? And if a kingdom be divided against itself, that kingdom cannot stand. And if a house be divided against itself, that house cannot stand. And if Satan rise up against himself, and be divided, he cannot stand, but hath an end. No man can enter into a strong man's house, and spoil his goods, except he will first bind (or deo) the strong man; and then he will spoil his house.”
Jesus said in the corresponding passage in Luke 11:20-22, “if I with the finger of God cast out devils, no doubt the kingdom of God is come upon you. When a strong man armed keepeth his palace, his goods are in peace: But when a stronger than he shall come upon him, and overcome him, he taketh from him all his armour wherein he trusted, and divideth his spoils.”
Here, Christ highlights the Sovereign power of the kingdom of God and reveals how the “strong man” – Satan – and his kingdom of devils can only be defeated by One that is stronger than them, namely Himself – the Son of God. As we examine the gospels we discover, Satan was stripped everywhere that Christ confronted him. The Lord entered the devil’s house and took authority over him and spoilt His goods. Previously, Satan's grip on the nations was so strong and so embedded that the truth of God's Word could not penetrate through. The devil overwhelmingly controlled the Gentile nations.