Sayyiduna Abdullah bin Amr (may Allah be pleased with him) narrates: Al-As bin Wa'il vowed in the Days of Ignorance that he would slaughter one hundred camels. Hisham bin al-As slaughtered fifty camels as his share. Sayyiduna Amr (may Allah be pleased with him) asked the Prophet (peace and blessings be upon him) about this, and the Prophet (peace and blessings be upon him) said: "If your father had affirmed the Oneness of Allah (tawhid), then if you fasted and gave charity on his behalf, that would benefit him."
Ahmad recorded it; its chain contains al-Hajjaj bin Artah, who is a mudallis (one who conceals defects in the chain).