(60) باب وَقْتِ رَكْعَتَىِ الْفَجْرِ وَذِكْرِ الاِخْتِلاَفِ عَلَى نَافِعٍ
It was narrated from Ibn 'Umar that Hafsah told him:
"When he was called to Subh prayer, the Messenger of Allah (ﷺ) would do two prostrations before Subh prayer." (ID)
Reference (ID): Sunan an-Nasa'i 1771 (ID)
In-book reference (ID): Book 20, Hadith 174 (ID)
English translation (ID): Vol. 2, Book 20, Hadith 1772 (ID)