Maliks Muwatta Book 15, Hadith Number 15.
Section : The Prostration of the Qur’an.
Yahya related to me from Malik from Ibn Shihab from al-Araj that Umar ibn al Khattab recited Surat an-Najm (Sura 53) and prostrated in it, and then got up and recited another sura.