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 or tens of times in the Sunnah prayers before Fajr and in the two Sunnah prayers after Maghrib.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5215