I saw the Prophet ﷺ, Abu Bakr, and Umar walking in front of the funeral procession.
حدثنا الحسن بن علي الخلال حدثنا عمرو بن عاصم عن همام عن منصور وبكر الكوفي وزياد وسفيان كلهم يذكر أنه سمعه من الزهري
رأيت النبي ﷺ وأبا بكر وعمر يمشون أمام الجنازة
[Its chain of transmission is hasan]. Nasai narrated it: 4/56, no. 1947 (Funerals, chapter on the position of the walker relative to the funeral procession), from the hadith of Hammam through this route, and Zuhri clearly stated that he heard it directly, according to his version. The hadith has corroborating narrations.