It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that once I observed for twenty-four or twenty-five days that the Prophet (peace and blessings be upon him) used to recite Surah Al-Kafirun and Surah Al-Ikhlas in the two rak'ahs (Sunnah) before Fajr and after Maghrib.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5699