Mukhtasar Muslim

Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings of Allah be upon him) said: "O Abu'l-Mundhir! Which verse in Allah's Book is the greatest with you?" I replied, "Allah and His Messenger (peace be upon him) know best." He (peace be upon him) said, "O Abu'l-Mundhir! Which verse in Allah's Book is the greatest with you?" I replied, "(Allah! There is no deity except Him, the Ever-Living, the Sustainer of [all] existence)" (i.e., Ayat al-Kursi). So the Messenger of Allah (peace be upon him) struck my chest (happily) with his hand and said, "O Abu'l-Mundhir! May knowledge be blessed for you."