(60) باب وَقْتِ رَكْعَتَىِ الْفَجْرِ وَذِكْرِ الاِخْتِلاَفِ عَلَى نَافِعٍ
It was narrated from Ibn 'Umar that Hafsah, the Mother of the Believers, :
Told him that when the Muaddhin fell silent, Allah's Messenger (ﷺ) would pray two brief rak'ahs. (ID)
Reference (ID): Sunan an-Nasa'i 1772 (ID)
In-book reference (ID): Book 20, Hadith 175 (ID)
English translation (ID): Vol. 2, Book 20, Hadith 1773 (ID)