The Greek word translated “bind” above is “deó,” and it means to “bind as in chains,” “put under obligation,” “prohibit or prevent from free movement or liberty.” When you study Revelation 20, the Bible tells us about Satan being bound and cast into the bottomless pit by an angel who came with chains. Furthermore, in the ninth chapter of the same Book, you’d read about how there were fallen angels who were bound in the River Euphrates, and the word came for them to be released, to be “loosed.” That wasn’t a mere permission and forbidding. Those fallen angels were bound, possibly with chains.
Also, in the Book of Luke chapter 13, we find a woman who, because she had been bound by Satan, was bowed over; she came in while Jesus was teaching in the Synagogue, and Jesus said, “Woman, you are loosed from your infirmity” (read Luke 13:12-16). The Master touched her and she straightened up, healed by the power of God. When Satan bound her, she couldn’t straighten herself. Therefore, when Jesus said, “…whatever you bind on earth will be bound in heaven,” He meant whatsoever you ask the Father in His (Jesus’) Name, the Father will give it to you.
So, when you say to Satan, “I bind you!” it has to be clear what you mean. What is it you want to bind? What do you understand by what you said? What does the devil understand by what you said? Your communication and intention must be clear. For instance, Jesus said to an evil spirit, “…Deaf and dumb spirit, I command you, come out of him and enter him no more!” (Mark 9:25). He bound the spirit from coming back into the young guy. He was very clear about his instruction to the devil and what He was forbidding him from. Therefore, when you want to bind an evil spirit, be clear as to what you want; and he won’t be able to withstand your command. Blessed be God!