It is narrated from Sayyiduna Abu Sa'id (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) called Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) while he was praying. When he finished the prayer, he met the Prophet (peace and blessings of Allah be upon him). The Messenger of Allah (peace and blessings of Allah be upon him) placed his hand on the hand of Sayyiduna Ubayy (may Allah be pleased with him), and he was about to leave through the door of the mosque. The Prophet (peace and blessings of Allah be upon him) said: "I wish that you do not leave through the door of the mosque until you learn a surah such that neither the Torah, nor the Gospel, nor the Qur'an has anything like it." Sayyiduna Ubayy (may Allah be pleased with him) said: So I walked slowly in hope of this. Then I said: O Messenger of Allah (peace and blessings of Allah be upon him)! Teach me the surah which you promised. The Prophet (peace and blessings of Allah be upon him) said: "How do you recite when you begin the prayer?" Sayyiduna Ubayy (may Allah be pleased with him) said: So I began to recite «﴿الْحَمْدُ لِلّٰهِ رَبِّ الْعَالَمِينَ﴾» until I finished the surah. The Messenger of Allah (peace and blessings of Allah be upon him) said: "It is this surah, and this surah is the Sab‘ al-Mathani and the Great Qur'an which I have been given."