The devil has already been defeated but he is still trying to cause as much grief as he can. For this reason he is called the evil one. The word evil means to cause grief and the Bible says that hell is one of the things that is never satisfied. Sheol is another word for hell.
Proverbs 27:20a Sheol and Abaddon are never satisfied,
Satan is going to be cast into hell with all the demons and he is trying to take as many people as possible.
Matthew 25:41 Then He will also say to those on His left, ‘Depart from Me, accursed ones, into the eternal fire which has been prepared for the devil and his angels;
As mentioned earlier the devil was defeated when Christ went to the cross. This was spoken of in Genesis and is the first reference to Jesus Christ coming. He came to bruise the devil on the head.
Genesis 3:15 And I will put enmity
Between you and the woman,
And between your seed and her seed;
He shall bruise you on the head,
And you shall bruise him on the heel.”
The Bible says that the devil roams to and fro throughout the earth looking for someone to destroy.
I Peter 5:8 Be of sober spirit, be on the alert. Your adversary, the devil, prowls around like a roaring lion, seeking someone to devour.
Satan comes like a thief, when you least expect him and when you are at a weak moment. If he can not rob you of salvation then he will seek to rob you of your joy and cause you to be a defeated Christian. Christians are defeated when they compromise.
John 10:10a The thief comes only to steal and kill and destroy;
Christians are useless in the kingdom of God when they compromise. A stream that has been trampled by animals is worthless to drink out of and so is a polluted well.
Proverbs 25:26 Like a trampled spring and a polluted well is a righteous man who gives way before the wicked.
However, the Lord tells us to resist the devil and he will flee.
I Peter 5:9 But resist him, firm in your faith, knowing that the same experiences of suffering are being accomplished by your brethren who are in the world.
We resist the devil through the Word of God. It is the sword of the Spirit and Jesus Himself used the Word of God when He was tempted by the devil.
Matthew 4:3-10 And the tempter came and said to Him, “If You are the Son of God, command that these stones become bread.” But He answered and said, “It is written, ‘Man shall not live on bread alone, but on every word that proceeds out of the mouth of God.’” Then the devil *took Him into the holy city and had Him stand on the pinnacle of the temple, and *said to Him, “If You are the Son of God, throw Yourself down; for it is written, ‘He will command His angels concerning You’; and‘On their hands they will bear You up, So that You will not strike Your foot against a stone.’”Jesus said to him, “On the other hand, it is written, ‘You shall not put the Lord your God to the test.’”Again, the devil took Him to a very high mountain and showed Him all the kingdoms of the world and their glory; and he said to Him, “All these things I will give You, if You fall down and worship me.” Then Jesus said to him, “Go, Satan! For it is written, ‘You shall worship the Lord your God, and serve Him only.’”
After you have suffered a little while then the Lord Himself will come to you and comfort you. Resist the devil by keeping firm in your faith and standing on the Word of God. Don’t compromise. Cry out to the Lord to help you. Quote the Word of God out loud or read it out loud.
I Peter 5:10 After you have suffered for a little while, the God of all grace, who called you to His eternal glory in Christ, will Himself perfect, confirm, strengthen and establish you.
After you have seen His love and faithfulness you will be strengthened in your faith and now you are to strengthen and encourage other Christians. We need each other.
Luke 22:31,32 Simon, Simon, behold, Satan has demanded permission to sift you like wheat; but I have prayed for you, that your faith may not fail; and you, when once you have turned again, strengthen your brothers.”
Jesus is praying for you that your faith will not fail.