Bilal narrated that he came to the Prophet ﷺ to call him for the dawn prayer, but Ayesha kept Bilal occupied with a question she was asking him until the daylight became clear and morning had truly broken.Bilal then stood and called him for the prayer, repeating the call, but the Messenger of Allah ﷺ did not come out. When he finally came out and led the people in prayer, Bilal informed him that Ayesha had occupied him with a question she had asked, until it had become full daylight, and then he had been slow in coming out.The Prophet ﷺ said, "I was praying the two units of the Fajr sunnah."Bilal said, "Messenger of Allah, it had truly become daylight."He replied, "Even if it had become much more daylight than it was, I would still have prayed those two units, and prayed them well and beautifully."
حدثنا أبو المغيرة حدثنا عبد الله بن العلاء حدثني أبو زياد عبيد الله بن زياد الكندي
أنه حدثه أنه أتى النبي ﷺ يؤذنه بصلاة الغداة فشغلت عائشة بلالا بأمر سألته عنه حتى فضحه الصبح وأصبح جدا قال فقام بلال فآذنه بالصلاة وتابع بين أذانه فلم يخرج رسول الله ﷺ فلما خرج فصلى بالناس أخبره أن عائشة شغلته بأمر سألته عنه حتى أصبح جدا ثم إنه أبطأ عليه بالخروج فقال إني ركعت ركعتي الفجر قال يا رسول الله إنك قد أصبحت جدا قال لو أصبحت أكثر مما أصبحت فركعتهما وأحسنتهما وأجملتهما
Its isnad is sahih. Abdullah bin Ala is trustworthy, and his hadith is found in Bukhari. Ubayd bin Ziyad, or Ziyada, Kindi Dimashqi is trustworthy, and his hadith is found in Abu Dawud, 2/19, no. 1257, in the chapter on prayer, on shortening the two units of the Fajr prayer.