وَعَنْ أَبِي هُرَيْرَةَ
أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ سَمِعَ رَجُلًا يَقْرَأُ (قُلْ هُوَ اللَّهُ أَحَدٌ) فَقَالَ: «وَجَبَتْ» قُلْتُ: وَمَا وَجَبَتْ؟ قَالَ: «الْجنَّة»
The Prophet (sallallahu alayhi wa sallam), on hearing a man reciting “Say, He is God, One” remarked, “It is certain.” I asked him what was certain, and he replied that it was paradise. Malik, Tirmidhi and Nasai transmitted it.
Mishkat al-Masabih 2064, Book 9, The Excellent Qualities of the Qur'an, Hadith 50. 1 min read