It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that a man used to clean the mosque; he died, or (the woman) died. When he (peace and blessings be upon him) missed that person, he (peace and blessings be upon him) asked: "What happened to that person who used to serve the mosque?" It was said: That person has died. He (peace and blessings be upon him) said: "Why did you not inform me?" They said: It was night. He (peace and blessings be upon him) said: "Show me the grave." He (peace and blessings be upon him) came to the grave and offered the funeral prayer. Then Thabit (may Allah have mercy on him) also mentioned that he (peace and blessings be upon him) said: "These graves are filled with darkness, and Allah Almighty illuminates them through my prayer."
What seems most likely is that this addition belongs to a narration other than that of Abu Rafi' from Abu Hurayrah: either it is from Thabit from the Prophet (peace and blessings be upon him), mursal, as Ahmad bin Abdah and those who corroborated him narrated it, or from Thabit from Anas from the Prophet (peace and blessings be upon him), as Khalid bin Khidash narrated it. Others besides Hammad narrated it from Thabit from Abu Rafi' and did not mention it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 7015