Answered by Shaykh Yūsuf Badāt
When I was reciting a sūrah (Qur’ānic chapter) yesterday I had a waswasah (evil thought) that reciting this verse will make one a disbeliever, astaghfirullāh (I seek refuge in God). After a few hours I get the doubt whether I said these words with my tongue or not. My question is, is it considered as kufr (disbelief) if a person says this accidentally without intending to do kufr of God’s book?
بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ
In the Name of God, Most Merciful, Most Kind
Thank you/ Jazāk Allāh Khayr for contacting Mathabah with your query.
In response to your question, kindly note that your thought is from waswasah (a devilish insinuation). As long as you did not believe in it with conviction, your thought or statement will not result in committing kufr (disbelief).
“And if it comes to you from the devil an evil suggestion, then seek refuge in God. Indeed, He is the All-Hearing and All-Knowing.” – (Qurʿān: 41:36).
The Prophet (peace and blessings upon him) said, “I bear testimony to the fact that there is no god but Allāh, and I am His Messenger. The person who would meet God without entertaining any doubt about these [two fundamentals] would enter Paradise”. – (Ṣaḥīḥ Muslim 27) 
The Prophet (peace and blessings be upon him) said, “God has forgiven my followers the evil thoughts that occur in their minds, as long as such thoughts are not put into action or uttered.” – (Ṣaḥīḥ Bukhārī 5269) 
Only Allāh knows best
 وَإِمَّا يَنزَغَنَّكَ مِنَ الشَّيْطَانِ نَزْغٌ فَاسْتَعِذْ بِاللَّه – حم فصلت ۖ إِنَّهُ هُوَ السَّمِيعُ الْعَلِيمُ
 فَقَالَ عِنْدَ ذَلِكَ “ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنِّي رَسُولُ اللَّهِ لاَ يَلْقَى اللَّهَ بِهِمَا عَبْدٌ غَيْرَ شَاكٍّ فِيهِمَا إِلاَّ دَخَلَ الْجَنَّةَ ” – رواه مسلم ٢٧ .
 عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ “ إِنَّ اللَّهَ تَجَاوَزَ عَنْ أُمَّتِي مَا حَدَّثَتْ بِهِ أَنْفُسَهَا، مَا لَمْ تَعْمَلْ أَوْ تَتَكَلَّمْ ” – رواه البخاري ٥٢٦٩.