The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
20/60. Chapter:
The time for the two rak'ahs of Fajr, and mentioning the differences reported from Nafi'
Sunan an-Nasai
أَخْبَرَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، قَالَ أَنْبَأَنَا يَحْيَى، قَالَ حَدَّثَنَا الأَوْزَاعِيُّ، قَالَ حَدَّثَنِي يَحْيَى، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنْ حَفْصَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَرْكَعُ بَيْنَ النِّدَاءِ وَالصَّلاَةِ رَكْعَتَيْنِ خَفِيفَتَيْنِ .
It was narrated from Ibn 'Umar that Hafsah said: "The Messenger of Allah (ﷺ) used to pray two brief rak'ahs between the call (the Adhan) and the prayer."
Reference : Sunan an-Nasa'i 1767In-book reference : Book 20, Hadith 170English translation : Vol. 2, Book 20, Hadith 1768