Maliks Muwatta Book 16, Hadith Number 8.
Section : Walking in Front of the Bier.
Yahya related to me from Malik from Ibn Shihab that the Messenger of Allah, may Allah bless him and grant him peace, and Abu Bakr and Umar as well as the khalifas up until this time and Abdullah ibn Umar, would walk in front of the bier.