The prayers of other Muslims on behalf of the dead will benefit the dead. In chapter al-Hashr (59):10, Allaah praises the believers who pray for those who have passed away before their time. Furthermore, the funeral prayer itself consists mostly of prayers for the dead. Safwaan said: I visited Abud-Dardaa’s home in Syria, but did not find him there. Ummud-Dardaa asked [me]: Are you going to make Hajj this year? I said yes and she said: Pray to Allaah for good for us, for the Prophet (PBUH) said: “The prayer of a Muslim for his brother Muslim in his absence will be answered. There is an assigned angel near his head who says: ‘Amen and may the same be for you,’ as long as he prays for the good of his brother.” I left and went to the market place where I met Abud-Dardaa and he related from the Prophet (PBUH) the same as that. Sahih Muslim, vol.4, p.1429, no.6590.