Musannaf Ibn Abi Shayba 3:2012

Waki’ and al-Fadl ibn Dukayn narrated to us, from Abu Hilal, from Anas ibn Sirin, that Ibn Mas’ud used to recite in the Dhuhr prayer "Alif-Lam-Mim Tanzil al-Sajdah" (Surah as-Sajdah). And in the other (rak'ah), he would recite a surah from the Mathani.