It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) called Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) while he was standing in prayer, and he did not answer. He (peace and blessings be upon him) said: "O Ubayy, what prevented you from answering me?" He said: "I was praying." He (peace and blessings be upon him) said: "Has Allah, the Blessed and Exalted, not said: 'Respond to Allah and to the Messenger when he calls you' [Surah al-Anfal: 24] ? Do not leave the mosque until I teach you a surah the like of which Allah did not reveal in the Torah, the Gospel or the Psalms." Ubayy said: Then he (peace and blessings be upon him) leaned on my hand, until, when he reached the far end of the mosque, I said: "O Prophet of Allah, you said such-and-such." He (peace and blessings be upon him) said: "Yes, it is the Mother of the Qur'an (Umm al-Qur'an). By the One in whose hand my soul is, Allah did not reveal the like of it in the Torah, the Gospel or the Psalms. It is (equivalent to) the seven long surahs that I have been given, and it is the Great Qur'an." [Surah al-Hijr: 87]