Maliks Muwatta Book 15, Hadith Number 18.

Yahya related to me from Malik from Ubaydullah ibn Abd ar-Rahman that Ubayd ibn Hunayn, the mawla of the family of Zayd ibn al Khattab, said that he had heard Abu Hurayra say, “I was going along with the Messenger of Allah, may Allah bless him and grant him peace, when he heard a man reciting Surat al-Ikhlas (Sura 112). The Messenger of Allah, may Allah bless him and grant him peace, said, ‘It is obligatory,’ and I asked him, ‘What is, Messenger of Allah?’ and he said, ‘The Garden.’ I wanted to tell the man the good news but I was afraid that I would miss the midday meal with the Messenger of Allah, may Allah bless him and grant him peace, and I preferred to eat with the Messenger of Allah, may Allah bless him and grant him peace. When I went to the man afterwards I found that he had gone.”