Aisha reported that whenever dawn broke, the Messenger of Allah ﷺ would pray only two brief units of prayer.
أخبرنا أحمد بن عبد الله بن الحكم قال حدثنا محمد بن جعفر قال حدثنا شعبة عن زيد بن محمد قال سمعت نافعا يحدث عن ابن عمر
أنها قالت كان رسول الله ﷺ إذا طلع الفجر لا يصلي إلا ركعتين خفيفتين
Recorded by Muslim in "Prayer of the Traveler," chapter on the recommendation of the two sunnah rakahs of Fajr and encouragement to perform them, from Abdullah, and by Bukhari, "Adhan," chapter on the adhan after Fajr, no. 618, and Ahmad bin... , no. 723, from the hadith of Nafi, and it is also in Kubra, no. 1559.