Ibn 'Umar (May Allah be pleased with them) reported:
I observed the Prophet (ﷺ) for one month reciting in the two supererogatory Rak'ah of the Fajr prayer Surat Al-Kafirun (No. 109) [in the first Rak'ah], and Surat Al-Ikhlas (No. 112) [in the second Rak'ah].[At-Tirmidhi]. (JA)
App reference (JA): Book 9, Hadith 119 (JA)
Arabic/English book reference (JA): Book 9, Hadith 1109 (JA)