Suhayl bin Abi Salih narrates from his father, from Sayyiduna Abu Sa'id (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "When you walk with a funeral, do not sit until it is set down."
Suhayl said: I saw Abu Salih; he would not sit until (the funeral) had been taken down from the men's shoulders. Al-Thawri narrated this hadith from Suhayl, from his father, from Sayyiduna Abu Hurayrah (may Allah be pleased with him), saying in it: "until it is placed on the ground." Abu Mu'awiyah narrated from Suhayl: "until it is placed in the lahd (niche of the grave)." And Sufyan (al-Thawri) has better memory than Abu Mu'awiyah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6875