Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates: I saw the Messenger of Allah (peace and blessings be upon him) more than twenty-five times, or he said: more than twenty times, reciting "Qul ya ayyuha al-kafirun" and "Qul huwa Allahu ahad" in the two rak'ahs of Fajr.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13470