The son of Abd al-Rahman bin Abza narrates from his father (may Allah be pleased with him) that Abu Bakr and Umar (may Allah be pleased with them both) used to walk in front of the funeral, and Ali (may Allah be pleased with him) used to walk behind it. It was said to Ali (may Allah be pleased with him): They both (al-Siddiq and al-Faruq, may Allah be pleased with them both) walk in front of the funeral? He said: They know that walking behind it is better than walking in front of it, just as a man's prayer in congregation is better than his praying alone; but they are easy-going and make things easy for the people.
This Za'idah is Ibn Khirash, and it is also said Ibn Aws bin Khirash al-Kindi; he narrates this hadith from Sa'id bin Abd al-Rahman bin Abza. The reports about walking in front of it are more authentic and more numerous, and success is from Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6868