Sunan an-Nasa'i 543
سنن النسائي#543Sahihأَخْبَرَنَا إِبْرَاهِيمُ بْنُ هَارُونَ، قَالَ حَدَّثَنَا حَاتِمُ بْنُ إِسْمَاعِيلَ، قَالَ حَدَّثَنَا جَعْفَرُ بْنُ مُحَمَّدِ بْنِ عَلِيِّ بْنِ الْحُسَيْنِ، عَنْ أَبِيهِ، أَنَّ جَابِرَ بْنَ عَبْدِ اللَّهِ، قَالَ صَلَّى رَسُولُ اللَّهِ صلى الله عليه وسلم الصُّبْحَ حِينَ تَبَيَّنَ لَهُ الصُّبْحُ .
Ja'far bin Muhammad bin 'Ali bin Al-Husain narrated from his father, that Jabir bin 'Abdullah said:"The Messenger of Allah (ﷺ) prayed Subh as soon as he was certain the dawn had appeared
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: 6:50