It was mentioned in the texts of the Qur'an and the Sunnah some Adhkar and useful invocations that expel Satan and keep it away from a person. By keeping to them, a person shall be in an immune fort that will protect him -by the will of Allah- from the accursed Satan. So, he will not be able to approach a person for harm or insinuation because there is no power for Satan over the person who keeps to Adhkar and obeys his Lord, but his power shall be over those who follow him and over those who listen to his insinuations.
Therefore, it is better for a believer to keep to Adhkar and invocations that were reported in the Shari`ah to protect himself from Satan and his plots and evil. Allah (Glory be to Him) says: "And say: My Lord! I seek refuge with You from the whisperings (suggestions) of the Shayâtîn (devils). * And I seek refuge with You, My Lord! lest they should come near me." [Surat Al Mu'minun: 97 - 98]. Allah (may He be Exalted) says: "And if an evil whisper from Shaitân (Satan) tries to turn you away (from doing good), then seek refuge in Allâh. Verily, He is the All-Hearer, the All-Knower." [Surat Fussilat: 36].
The meaning of Isti`adhah is to ask for help: I resort to Him and seek His Forgiveness to protect me from Satan and of his evil. Whoever seeks refuge in Allah, Allah protects him and who holds fast with Him shall be guided to a Straight Path, hence, asking the protection of Allah expels Satan and fortifies a person.
Imam Muslim reported in his Sahih on the authority of Abu Ad-Darda' (may Allah be pleased with him) who said: "The Messenger of Allah (peace be upon him) stood up (to pray) and we heard him saying: "I seek refuge in Allah from you." Then said: "I curse you with Allah's Curse" three times, then he stretched out his hand as though he was taking hold of something. When he finished Salah, we said: O Messenger of Allah, we heard you saying something during Salah which we have not heard you saying before, and we saw you stretching out your hand. He replied: Allah's enemy Satan came with a flame of fire to put it in my face, so I said three times:" I Seek refuge in Allah from you." Then I said three times:" I curse you with Allah's full curse." But he did not retreat (on any one of these) three occasions. Thereafter I meant to seize him. I swear by Allah that had it not been for the supplication of my brother Sulayman he would have been bound, and made an object of sport for the children of Medina." [Sahih Muslim No. 542].
Imam Muslim also reported on the authority of `Uthman ibn Abu Al `As Ath-Thaqafy (may Allah be pleased with him) that he came to the prophet (peace be upon him) and said: "Satan intervenes between me and my Salah and my recitation of the Qur'an and he confounds me. Upon this, the Messenger of Allah (may peace and blessings be upon him) remarked: That is (the doing of the Satan) who is known as Khinzab, and when you perceive its effect, seek refuge with Allah from it and spit three times to your left. He said: I did that and Allah dispelled that from me." [Sahih Muslim No. 2203].
It was reported in Sahih Al Bukhari and Sahih Muslim on the authority of Abu Hurayrah (may Allah be pleased with him) who said: The Messenger of Allah (peace be upon him) said: "Satan comes to one of you and says: Who created so-and-so? Who created so-and-so? until he says: Who has created your Lord? When he inspires such a question, one should seek refuge with Allah and give up such thoughts." [Sahih Al Bukhari, No. 3276 and Sahih Muslim No. 134].
These texts are crystal-clear to the greatness of asking for the protection of Allah, it expels Satan, protects a person from him, and a person shall be safe of Satan's insinuations and evil.
Of the things which expel Satan is Adhan and when Satan hears Adhan, he escapes. It was reported in Sahih Al Bukhari and Sahih Muslim on the authority of Abu Hurayrah (may Allah be pleased with him) who said that the Messenger of Allah (peace be upon him) said: "When the Adhan is pronounced Satan takes to his heels and passes wind with noise during his flight in order not to hear the Adhan. When the Adhan is completed he comes back and again takes to his heels when the Iqamah is pronounced." [Sahih Al Bukhari, No. 608 and Sahih Muslim No. 389].
It was reported in Sahih Muslim on the authority of Suhayl ibn Abu Salih who said: "My father sent me to Banu Harithah along with a boy or a man. Someone called him by his name from an enclosure. He (the narrator) said: The person with me looked towards the enclosure, but saw nothing. I made a mention of that to my father. He said: If I knew that you would meet such a situation I would have never sent you (there), but (bear in mind) whenever you hear such a call (from the evil spirits) pronounce the Adhan for I have heard Abu Hurayrah saying that the Messenger of Allah (peace be upon him) said: Whenever Adhan is proclaimed, Satan runs back vehemently." [Sahih Muslim No. 389].
Of the things that protect a person from Satan is frequent mentioning of Allah in all conditions: Upon entering, upon getting out, upon riding, upon going to sleep, and so on. Allah (Glory be to Him) says: "Verily, those who are Al-Muttaqûn (the pious), when an evil thought comes to them from Shaitân (Satan), they remember (Allâh), and (indeed) they then see (aright)." [Surat Al A`raf: 201]. Allah also says: "And whosoever turns away blindly from the remembrance of the Most Gracious (Allâh) (i.e. this Qur'ân and worship of Allâh), We appoint for him Shaitân (Satan - devil) to be a Qarîn (a companion) to him." [Surat Az-Zukhruf: 36].
It was reported in Sunan At-Tirmidhy and Al Musnad with an authentic chain of narration on the authority of Al Harith Al Ash`ary that the Prophet (peace be upon him) said: Allah commanded the Prophet Yahya ibn Zakariya (John AS) with five things that he may abide by them and command the Banu Isra’il (children of Isra’il) to abide by them. But he delayed in conveying them. The Prophet `Esa (Jesus AS) said to him: "Allah commanded you with five commands that you may abide by them and command Banu Isra’il to abide by them. So, either you give them these commands, or I will do that.” So Yahya said: “If you take precedence over me in conveying them, I fear that I will be swallowed up (in earth) or punished.” So, he assembled the people in Bayt al-Maqdis and it was filled up, and people sat down on elevated places. He said to them, “Allah has commanded me with five commands that I should abide by them and command you to abide by them. (1) The first of them is that you worship Allah and associate not anything with Him (that means do not take anyone or anything equal to Him). And the example of one who associates someone or something with Allah is like a man who bought a slave with his pure earnings of gold or silver and said to him: ‘This is my house and this is my business. So, take up this occupation and pay me what you earn’. He works but pays to another than his master. So, which of you will be pleased to have a slave like that? (2) And Allah commands you to offer Salah. When you offer Salah, do not turn elsewhere, for Allah has His face towards His slave who offers Salah as long as he does not turn elsewhere. (3) And I command you to keep fast. Its similitude is of a man who is with a party. He has a bagful of musk. All of them are pleased with it or he is pleased with its odor. And the odor of one who is fasting is more pleasant to Allah than the odor of musk. (4) And I command you to give charity. Its similitude is like that of a man who is imprisoned by his enemy. They tie his hand to his neck and take him to be executed. He offers, I pay ransom to you the little or much, and he ransoms himself from them, (5) And, I command you that you remember Allah. The similitude for that is like a man whose enemy pursues him in haste while he comes to a strong fort and protects him-self from them. So is the man whom nothing protects from the devil but Dhikr (remembrance) of Allah.” The Prophet (peace be upon him) said: “And I command you with five commands with which Allah has commanded me. They are, to hear, to obey, to wage jihad, to make Hijrah (migration) and to be attached to the main body of Muslims, for he who separates from the main body even by a span takes out the rope of Islam from his neck unless he returns to it. And, he who invites people to the evils of the Pre-Islamic Period is fuel of Hell.” Someone asked: “O Messenger of Allah (peace be upon him), even if he offered Salah and kept fast”? He said: “Even if he offered Salah and fasted. So invite to Allah Who named you Muslims, Believers and Slaves of Allah." [Sunan At-Tirmidhy No. 2863 and Musnad Imam Ahmad 4/130, and Al Albany (may Allah bestow mercy on his soul) graded it as authentic in Sahih Al Jami` No. 1724].
It was reported in Sahih Muslim on the authority of Jabir (may Allah be pleased with him) that the Prophet (peace be upon him) said: "When night falls, then keep your children close to you, for the devil spread out then. An hour later you can let them free; and close the gates of your house (at night), and mention Allah's Name thereupon, and cover your utensils, and mention Allah's Name thereupon, (and if you don't have something to cover your utensil) you may put across it something (e.g. a piece of wood etc.)." [Sahih Muslim No. 2012].
When a Muslim is grateful to his lord in all his conditions, he shall be safe of the harm of Satan, so neither his insinuations nor his evil can harm a person as was mentioned in the above Ayah: "And say: My Lord! I seek refuge with You from the whisperings (suggestions) of the Shayâtîn (devils). * And I seek refuge with You, My Lord! lest they should come near me." [Surat Al Mu'minun: 97 - 98].
Indeed, we have mentioned many kinds of Adhakr which protect a person from Satan such as mentioning the name of Allah upon entering one's house, upon eating food, reciting Ayatul-Kursy when a person goes to bed and when he does so, a protector from Allah shall preserve him until he wakes up. Whoever says in the morning: "La Ilaha Illa Allah Wahdahu La Sharika Lah, Lahu Al Mulku wa Lahu Al Hamdu wa Huwa `Ala Kulli Shay'in Qadir [No god but Allah alone who has no partner. To him belong the dominion and to Him is all praise and He is Able above everything]," ten times shall be protected from Satan until the evening. And whoever says it in the evening shall be protected from Satan until the morning. Whoever recites the last two Ayahs of Surat Al Baqarah in the evening, they will be enough for him from every evil and from the evil of Satan. When a Muslim says upon going out from home: "Bismillah Tawakkaltu `Ala Allah La Hawla wa l Quwwata Illa Billah [In the name of Allah, I relay on Him, there is no might nor strength save in Allah]," Satan shall walk away. In addition to other blessed Adhkar reported in the Sunnah of the Prophet (peace be upon him).