Sayyiduna Abdullah bin Malik bin Buhaynah (may Allah be pleased with him) states: Once the Prophet (peace and blessings be upon him) was sitting among his Companions, when he (peace and blessings be upon him) said: "May Allah Almighty send down mercy upon the people of that graveyard." He (peace and blessings be upon him) said these words three times. The narrator says: We could not tell which graveyard the Prophet (peace and blessings be upon him) meant, and the Prophet (peace and blessings be upon him) had not mentioned any name concerning them. The narrator states: Then one of the Companions of the Prophet (peace and blessings be upon him) went to one of the honoured wives of the Prophet (peace and blessings be upon him). The narrator Attaf says: I was told that this honoured wife was Sayyidah Aishah Siddiqah (may Allah be pleased with her). That Companion said to Sayyidah Aishah (may Allah be pleased with her): "the Prophet (peace and blessings be upon him) mentioned the people of a certain graveyard and prayed for mercy for them, but he did not tell us which graveyard it is." When the Prophet (peace and blessings be upon him) came to Sayyidah Aishah (may Allah be pleased with her), Sayyidah Aishah (may Allah be pleased with her) asked the Prophet (peace and blessings be upon him) about that graveyard. the Prophet (peace and blessings be upon him) said: "The people of the graveyard of Asqalan (that is, it was for them that I made that supplication)."
Abu Ya'la and al-Bazzar recorded it, and his wording is: the Prophet (peace and blessings be upon him) prayed for forgiveness for the people of the graveyard of Asqalan and prayed for mercy for them. In Abu Ya'la's chain there is a narrator, Ali bin Abdullah bin Malik bin Buhaynah, and in al-Bazzar's chain the narrator's name is Malik bin Abdullah bin Buhaynah, and I do not know either of them; the rest of the narrators are thiqat (trustworthy). There is a slight difference of opinion about some of its narrators.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 16667