(Full text is here: http://www.desiringgod.org/ResourceLibrary/AskPastorJohn/ByTitle/3419_Why_does_God_allow_Satan_to_live/
"Why does God allow Satan to live?"
"The Bible doesn't answer why directly, so we have to go on inferences. But here is my best shot:
God has ordained that Satan have a long leash—with God holding onto it—because he knows that when we walk in and out of those temptations, struggling both with the physical and moral effects that they bring, more of God's glory will shine in that battle than if he took Satan out yesterday.
There will be evidences of God's patience with us and of his mercy towards us as we struggle with sin. And there will be evidences of his sustaining grace as we go through horrific physical suffering that Satan was the immediate cause of (as it says in the Bible: "This woman . . . whom Satan bound for eighteen years" [Luke 13:16]. She had this bent-over back, and Satan was doing it, and God was ordaining that he be allowed to do it). God ordains all of these things so that his glory—his mercy, justice, grace, wisdom—would shine more brightly....
Perhaps the other thing I should say is that he sent his Son right into the middle of this satanic warfare. It was Satan that put it into the heart of Judas to betray him. So Jesus exposes himself to the horrors of Satan's deceit and lies and murder—"He was a murderer from the beginning . . . [and] a liar" (John 8:44)—and dies, in order to make a public display of the principalities and powers in his defeat of them (Colossians 2:15).
There is more glory that will come to Jesus Christ by his suffering to destroy Satan than by powerfully shooting Satan in the head. And there is more glory that will come to Jesus Christ by our sharing in the sufferings of Christ—holding onto his supreme value—than if we had been able to say, "Satan, Depart!" and never have another problem.
And I think the reason for that—this is my ultimate final answer—is that the glory of God and Christ shines more brightly when we are seen to be supremely satisfied in Christ in spite of Satan's torments, rather than if we had his torments removed and liked Jesus because of it.
It's when you love Jesus in spite of Satan's torments and through them that his glory shines most brightly, rather than when we have life made easier for us by Satan's removal and we like Jesus because of it. " -John Piper
Listening to this got me thinking, as always, about whether or not I really love Jesus for Jesus sake. Do I love Him because He has poured out His blessings upon me or do I love Him truly for His own glory regardless of what that means for how privileged and blessed I am in this lifetime? If everything was taken from me, like Job, if I had no family, no husband, no stability, no career, no income, no opportunities would I really love Jesus? Probably not. I get fairly pouty with Him even when things are inconvenient.
Thank God for grace. I don't have to love Jesus perfectly and maybe I never will in this lifetime. But, it is not my love for Him that saves me. It's His for me.
"My faith is like sinking sand, changed by every wave.
My faith is like sinking sand, so I stand forever on grace."