Sunan an-Nasa'i 1771
سنن النسائي#1771Sahihأَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَبْدِ الْحَكَمِ، قَالَ أَنْبَأَنَا إِسْحَاقُ بْنُ الْفُرَاتِ، عَنْ يَحْيَى بْنِ أَيُّوبَ، قَالَ حَدَّثَنِي يَحْيَى بْنُ سَعِيدٍ، قَالَ أَنْبَأَنَا نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنْ حَفْصَةَ، أَنَّهَا أَخْبَرَتْهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا نُودِيَ لِصَلاَةِ الصُّبْحِ سَجَدَ سَجْدَتَيْنِ قَبْلَ صَلاَةِ الصُّبْحِ .
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
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 20:174