Reference: ad-Durar an-Naadhirah fil-Fataaawa al-Mu’aasirah – Page 677
Ibraaheem Aal ash-Shaykh – ad-Da’wah 1576, Ramadhaan 1417AH
Question: What is the ruling regarding the [group] supplication for the deceased in the graveyard after the burial and the saying of aameen thereafter?
Response: It is from the Sunnah that those who have followed the funeral [procession] stand by the graveside after the burial and individually supplicate for the deceased with mercy, forgiveness and firmness [in responding to the questions in the grave]. As for the group supplication or the saying of aameen after the supplication of one of those present, then this is not from the Sunnah and the Prophet (sal-Allaahu ‘alayhi wa sallam) would say:
«Seek forgiveness for your brother and ask [Allaah] to make him firm as he is now being questioned [in the grave]»