مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 1163
Prayer
The sunan prayers and their virtues - Section 1
وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: لَمْ يَكُنِ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَلَى شَيْءٍ مِنَ النَّوَافِلِ أَشَدَّ تَعَاهُدًا مِنْهُ على رَكْعَتي الْفجْر
‘A’isha said that the Prophet (ﷺ) was more particular about observing the two supererogatory rak'as at dawn than about observing any of the other supererogatory prayers. (Bukhari and Muslim.)
Mishkat al-Masabih, 1163مُتَّفَقٌ عَلَيْهِ (الألباني)