I observed the Prophet ﷺ for a month, and he would recite in the two rakahs before the dawn prayer "Say, O disbelievers" [Kafirun 109:1] and "Say, He is Allah, the One" [Ikhlas 112:1].
رمقت النبي ﷺ شهرا، فكان يقرأ في الركعتين قبل الفجر: {قل يايها الكفرون} و {قل هو الله أحد}.
Tirmidhi (417) and Ibn Majah (1149) both narrated it through Abu Ahmad Zubayri, who said, we were told by Sufyan, from Abu Ishaq, from Mujahid, from Ibn Umar, and he related it. Tirmidhi said, "The hadith of Ibn Umar is a hasan hadith. We do not know it as a narration of Thawri from Abu Ishaq except through the narration of Abu Ahmad, and what is well known among people is the narration of Israil from Abu Ishaq. This hadith has also been narrated from Abu Ahmad through Israil. Abu Ahmad Zubayri is trustworthy and a master of memorization. I heard Bundar say, 'I have not seen anyone with a better memory than Abu Ahmad Zubayri.' Abu Ahmad's name is Muhammad bin Abdullah bin Zubayr, the Kufan, the Asadi." End of quote.Nasai (992) narrated it through another route, from Abul-Jawwab, who said, we were told by Ammar bin Raziq, from Abu Ishaq, from Ibrahim bin Muhajir, from Mujahid, from Ibn Umar, who said, "I watched the Messenger of Allah ﷺ twenty times reciting in the two rakahs after Maghrib and in the two rakahs before Fajr, "Say, O disbelievers" and "Say, He is Allah, the One"."Abul-Jawwab's name is Ahwas bin Jawwab, with the jim vowelled with fatha and the waw doubled, Dabbi. Ibn Main said he is trustworthy, and Abu Hatim said he is truthful. Ammar bin Raziq, with the diminutive form, was Dabbi or Taymi, and he was deemed trustworthy by Yahya bin Main and Abu Zura Razi, while Abu Hatim said, "There is no harm in him."