وَإِمَّا يَنزَغَنَّكَ مِنَ الشَّيْطَانِ نَزْغٌ فَاسْتَعِذْ بِاللَّهِ
And if an evil whisper from Shaytan tries to turn you away, then seek refuge in Allah.
means, the devils among men may be deceived by your kind treatment of him, but the devils among the Jinn, when they insinuate their evil whispers, cannot be dealt with except by seeking refuge with the Creator Who gave him power over you. If you seek refuge with Allah and turn to Him, He will stop him from harming you and bring his efforts to naught. When the Messenger of Allah stood up to pray, he would say;
أَعُوذُ بِاللهِ السَّمِيعِ الْعَلِيمِ مِنَ الشَّيْطَانِ الرَّجِيمِ مِنْ هَمْزِهِ وَنَفْخِهِ وَنَفْثِه
I seek refuge in Allah the All-Hearing, All-Knowing, from the accursed Shaytan and his evil insinuations, breath and impurity."
We have already stated that there is nothing like this in the Qur'an, apart from the passage in Surah Al-A`raf, where Allah says;
خُذِ الْعَفْوَ وَأْمُرْ بِالْعُرْفِ وَأَعْرِض عَنِ الْجَـهِلِينَ
وَإِمَّا يَنَزَغَنَّكَ مِنَ الشَّيْطَـنِ نَزْغٌ فَاسْتَعِذْ بِاللَّهِ إِنَّهُ سَمِيعٌ عَلِيمٌ
Show forgiveness, enjoin what is good, and turn away from the foolish. And if an evil whisper comes to you from Shaytan, then seek refuge with Allah. Verily, He is All-Hearer, All-Knower. (7;199-200)
and the passage in Surah Al-Mu'minun where Allah says;
ادْفَعْ بِالَّتِى هِىَ أَحْسَنُ السَّيِّيَةَ نَحْنُ أَعْلَمُ بِمَا يَصِفُونَ
وَقُلْ رَّبِّ أَعُوذُ بِكَ مِنْ هَمَزَاتِ الشَّيـطِينِ
وَأَعُوذُ بِكَ رَبِّ أَن يَحْضُرُونِ
Repel evil with that which is better. We are Best-Acquainted with the things they utter. And say;
"My Lord! I seek refuge with You from the whisperings of the Shayatin. And I seek refuge with You, My Lord! lest they should come near me." (23;96-98)
إِنَّهُ هُوَ السَّمِيعُ الْعَلِيمُ
Verily, He is the All-Hearer, the All-Knower.