It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) must have recited Surah Al-Kafiroon and Surah Al-Ikhlas dozens of times in the Sunnah prayers before Fajr.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4909