Abu Dawud Book 25, Hadith Number 3990.

Narated By Umm Salamah, Ummul Mu’minin : The Apostle of Allah (PBUH) used to recite: “In the name of Allah, the Cherisher and Sustainer of the worlds; most Gracious, most Merciful; Master of the Day of Judgment,” breaking its recitation into verses, one after another.

Abu Dawud said: I heard Ahmad (b. Hanbal) say: The early reading is: Maliki yawmi’l-din.