Ubayy b. Ka'b said: Allah’s Messenger (ﷺ) said: ”O Abu’ al-Mundhir, do you know the verse from the Book of Allah which, according to you, is the greatest?” I said: Allah and His Apostle (ﷺ) know best. He again said: ”Abu'l-Mundhir, do you know the verse from the Book of Allah which, according to you, is the greatest?” I said: Allah, there is no god but He, the Living, the Eternal (2:256). Thereupon he struck me on my breast and said: “May knowledge be pleasant for you, O Abu'l-Mundhir!” Sahih Muslim 810
In-book reference : Book 6, Hadith 313
do you know the verse from the Book of Allah which is the greatest
USC-MSA *** (English) reference : Book 4, Hadith 1768
عن أبي بن كعب رضي الله عنه قال، قال رسول الله صلى الله عليه وسلم: " يَا أَبَا الْمُنْذِرِ أَتَدْرِي أَىُّ آيَةٍ مِنْ كِتَابِ اللَّهِ مَعَكَ أَعْظَمُ “ . قَالَ قُلْتُ اللَّهُ وَرَسُولُهُ أَعْلَمُ . قَالَ ” يَا أَبَا الْمُنْذِرِ أَتَدْرِي أَىُّ آيَةٍ مِنْ كِتَابِ اللَّهِ مَعَكَ أَعْظَمُ " . قَالَ قُلْتُ اللَّهُ لاَ إِلَهَ إِلاَّ هُوَ الْحَىُّ الْقَيُّومُ . قَالَ فَضَرَبَ فِي صَدْرِي وَقَالَ " وَاللَّهِ لِيَهْنِكَ الْعِلْمُ أَبَا الْمُنْذِرِ " . صحيح مسلم حديث ٨١٠