The Messenger of Allah ﷺ asked, "Abu al-Mundhir, do you know which verse from the Book of Allah that you have is the greatest?"I replied, "Allah and His Messenger know best."He asked again, "Abu al-Mundhir, do you know which verse from the Book of Allah that you have is the greatest?"I answered, "Allah, there is no god but He, the Ever-Living, the Sustainer of all existence" [Baqarah 2:255].He struck me on the chest and said, "By Allah, may knowledge bring you joy, Abu al-Mundhir."
قال رسول الله ﷺ: يا أبا المنذر، أتدري أي آية من كتاب الله معك أعظم؟ قال: قلت: الله ورسوله أعلم. قال: يا أبا المنذر، أتدري أي آية من كتاب الله معك أعظم؟ قال: قلت: {الله لا إله إلا هو الحي القيوم} [البقرة: ٢٥٥] قال: فضرب في صدري، وقال: والله ليهنك العلم أبا المنذر.
Muslim narrated it in the Book of the Prayer of Travelers (258:810) from Abu Bakr bin Abu Shayba, from Abdul-Ala bin Abdul-Ala, from Jareeri, from Abu Saleel, from Abdullah bin Rabah Ansari, from Ubayy bin Kaab, who mentioned it.His saying, "May the knowledge bring you joy," means, may the knowledge be a source of joy and blessing for you.