It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) offered the funeral prayer over Sayyiduna Hamzah (may Allah be pleased with him) and said seven takbirs over him. No slain man was brought but that Sayyiduna Hamzah (may Allah be pleased with him) was with him and he (peace and blessings be upon him) offered the funeral prayer, until he had offered seventy-two (72) funeral prayers over him.
This is weak; when Muhammad bin Ishaq bin Yasar does not name the one from whom he narrates, his report is of no value.
Al-Hasan bin Umarah narrates from al-Hakam, from Miqsam, from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) offered the funeral prayer over the slain of Uhud; but al-Hasan bin Umarah is weak, and his narration cannot be taken as proof.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6807