Sunan an-Nasa'i, Hadith 1944 ⓘ
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.
أَخْبَرَنَا إِسْحَاقُ 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 .
also referenced under: Book 21, Hadith 128 (In-Book) & Volume 3, Book 21, Hadith 1946 (DarusSalam)