The Book of Prayer
Bulugh al-Maram #433
كتاب الصلاة
وَعَنْهَا قَالَتْ: «لَمْ يَكُنْ اَلنَّبِيُّ - صلى الله عليه وسلم -عَلَى شَيْءٍ مِنْ اَلنَّوَافِلِ أَشَدَّ تَعَاهُدًا مِنْهُ عَلَى رَكْعَتَيْ اَلْفَجْرِ» مُتَّفَقٌ عَلَيْهِ.
Narrated:
The Prophet (ﷺ) was more particular about offering the two (optional) Rak'at at dawn than he was about offering any of the other optional prayers.
وَعَنْهَا قَالَتْ : "لَمْ يَكُنْ اَلنَّبِيُّ - صلى الله عليه وسلم -عَلَى شَيْءٍ مِنْ اَلنَّوَافِلِ أَشَدَّ تَعَاهُدًا مِنْهُ عَلَى رَكْعَتَيْ اَلْفَجْرِ" مُتَّفَقٌ عَلَيْهِ .
The Prophet (ﷺ) was more particular about offering the two (optional) Rak'at at dawn than he was about offering any of the other optional prayers.
— Bulugh al-Maram, Hadith 433