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]. (DE)
App reference (DE): Book 9, Hadith 119 (DE)
Arabic/English book reference (DE): Book 9, Hadith 1109 (DE)