Sahih Muslim Book 4, Hadith Number 1793.

Chapter : “The Qur’an has been revealed in seven modes of “reading” and its meaning.

This Hadith has been narrated by A’mash with the same chain of transmitters in which (‘Abdullah b. Mas’ud) said: “I know the manners in which the Messenger of Allah (may peace be upon him) recited the two surahs in one rak’ah and then twenty surahs in ten rak’ahs.”