It wasnarrated that Ibn 'Umar said:
"I watched the Prophet (ﷺ) foramonth, and in the two Rak'ah before Fajr he used to recite: "Say:Oyou disbelievers!" [Al-Kafirun (109)] and "Say: Allah is One."[Al-Ikhlas (112)] (DE)
English reference (DE): Vol. 1, Book 5, Hadith 1149 (DE)
Arabic reference (DE): Book 5, Hadith 1203 (DE)