Sunan an-Nasa'i 1944
سنن النسائي#1944Hasanأَخْبَرَنَا إِسْحَاق�� بْنُ إِبْرَاهِيمَ، وَعَلِيُّ بْنُ حُجْرٍ، وَقُتَيْبَةُ، عَنْ سُفْيَانَ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، أَنَّهُ رَأَى رَسُولَ اللَّهِ صلى الله عليه وسلم وَأَبَا بَكْرٍ وَعُمَرَ رَضِيَ اللَّهُ عَنْهُمَا يَمْشُونَ أَمَامَ الْجَنَازَةِ .
It was narrated from Salim:That his father saw the Messenger of Allah, Abu Bakr and 'Umar, may Allah be pleased with them, walking in front of the Janazah
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:
Abu Ghuddah-
Zubair Ali ZaiHasan
In-book reference: 21:127