The Prophet ﷺ said, "Allah the Exalted revealed in His Book, mentioning a people who showed arrogance, saying, 'When it was said to them, There is no god but Allah, they would grow arrogant' [Saffat 37:35]. And He the Exalted said, 'When those who disbelieved had put into their hearts zealotry, the zealotry of ignorance, Allah sent down His tranquility upon His Messenger and upon the believers, and bound them to the word of piety, for they were most worthy of it and deserving of it'. This is the statement, There is no god but Allah, Muhammad is the Messenger of Allah, which the polytheists rejected out of arrogance on the day of Hudaybiyyah, the day the Messenger of Allah ﷺ drew up the treaty with them concerning the term of truce."
عن النبي ﷺ قال: أنزل الله تعالى في كتابه فذكر قوما استكبروا فقال: {إنهم كانوا إذا قيل لهم لا إله إلا الله يستكبرون} [الصافات: ٣٥] وقال تعالى: {إذ جعل الذين كفروا في قلوبهم الحمية حمية الجاهلية فأنزل الله سكينته على رسوله وعلى المؤمنين وألزمهم كلمة التقوى وكانوا أحق بها وأهلها} وهي لا إله إلا الله محمد رسول الله استكبر عنها المشركون يوم الحديبية يوم كاتبهم رسول الله ﷺ في قضية المدة.
Ibn Abu Hatim narrated it, as Ibn Kathir mentioned in his Tafsir (345/7), and Ibn Hibban (218), and Bayhaqi in Asma wa-Sifat (195, 196), all of them through routes from Ibn Shihab Zuhri, who said, "Saeed bin Musayab told me that Abu Hurairah informed him," then he mentioned it. Its isnad is sahih.Of similar meaning is what was narrated from Ubayy bin Kaab, that he heard the Messenger of Allah ﷺ say, regarding "and made them adhere to the word of righteousness" [Fath 48:26], he said, "There is no god but Allah." Tirmidhi narrated it (3265), and Abdullah bin Imam Ahmad in his additions to the Musnad (21255), both through the route of Hasan bin Qazaa Basri, who said, "Sufyan bin Habib told us, Shubah told us, from Thuwayr, from his father, from Tufayl bin Abu bin Kaab, from his father," then he mentioned it.In the isnad is Thuwayr, who is Ibn Abu Fakhita Kufi, and he is daif, except that it strengthens what came before it.From this it becomes clear that Ibn Kathir's statement regarding the aforementioned hadith of Abu Hurairah, that it is "interpolated from the words of Zuhri," is not beyond question.