Abu Ubaydah narrates from Sayyiduna Abdullah (may Allah be pleased with him) that he said: "When one of you follows a funeral, let him take hold of all the sides of the bier, for that is of the Sunnah; then after that, if he wishes, let him carry more or leave it." (These are the words of Abu Nu'aym's narration.)
The same is also narrated through another chain: "When one of you follows the funeral, let him take hold of all the sides of the bier; then after that, if he wishes, let him carry more or leave it."
Through another chain: Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said: "Whoever follows a funeral, let him carry all the sides of the bier, for that is of the Sunnah; then after that, if he wishes, let him carry more."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9563