Amr bin Murrah said: I heard Sa'id bin al-Musayyib narrating from Sayyiduna Umar (may Allah be pleased with him) that he said: "All of these takbirs used to be said, four as well as five. Then we agreed by consensus on four for the funeral."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6946
Abu Wa'il said that in the time of the Messenger of Allah (peace and blessings be upon him) seven, five and six takbirs used to be said, or he said: four. So Umar bin al-Khattab (may Allah be pleased with him) gathered the Companions, and each man reported what he had seen; then Umar bin al-Khattab (may Allah be pleased with him) united them on four takbirs, like the longest prayer.
Waki' narrated it from Sufyan with 'four' in place of 'six'. And in what Waki' narrated from Mis'ar, from Abd al-Malik bin Iyas al-Shaybani, from Ibrahim: the Companions of the Messenger of Allah (peace and blessings be upon him) gathered in the house of Abu Mas'ud al-Ansari (may Allah be pleased with him), and they agreed that the takbirs over the funeral are four.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6947
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that in the last funeral prayer that he (peace and blessings be upon him) offered, he said four takbirs.
Al-Nadr bin Abd al-Rahman Abu Umar al-Khazzaz is alone in narrating it from Ikrimah, and he is da'if (weak). This wording has been narrated through other routes as well, all of them weak; however, the agreement of most of the Companions (may Allah be pleased with them) on four is like evidence for it, and Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6948
Abd al-Rahman bin Abza (may Allah be pleased with him) said: I offered the funeral prayer with Umar (may Allah be pleased with him) over Zaynab (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), and he said four takbirs. Then he sent word to the wives of the Prophet (peace and blessings be upon him) asking who should place her in her grave, and Umar (may Allah be pleased with him) would have liked to place her in her grave himself. So they sent word to Umar (may Allah be pleased with him): the one who used to see her during her lifetime should place her in the grave. Umar (may Allah be pleased with him) said: They have spoken the truth.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6949
Umayr bin Sa'id said: I offered the funeral prayer over Ibn al-Mukaffaf behind Sayyiduna Ali bin Abi Talib (may Allah be pleased with him), and he said four takbirs. Then he came to his grave and said: 'Allahumma abduka wa waladu abdika nazala bika wa anta khayru manzulin bihi, Allahumma wassi' lahu mudkhalahu waghfir lahu dhanbahu, fa inna la na'lamu bihi illa khayran wa anta a'lamu bihi' (O Allah, this is Your servant and the son of Your servant; he has come to You as a guest, and You are the best of hosts. O Allah, make his grave spacious for him and forgive him his sins; we know nothing of him but good, and You know him better.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6950
Thabit bin Ubayd (may Allah have mercy on him) said: I offered the funeral prayer with Sayyiduna Zayd bin Thabit (may Allah be pleased with him) over his mother, and he said four takbirs over her. Imam al-Sha'bi (may Allah have mercy on him) narrates from Sayyiduna Zayd bin Thabit (may Allah be pleased with him) that he said four takbirs over his mother, and he did not grudge her any good.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6951
Al-Sha'bi (may Allah have mercy on him) said that Ibn Umar (may Allah be pleased with them both) offered the funeral prayer over Zayd bin Umar and his mother, Umm Kulthum bint Ali; he placed the man next to the imam and the woman behind him, and said four takbirs over them. Behind him were Ibn al-Hanafiyyah (may Allah have mercy on him), Husayn bin Ali (may Allah be pleased with them both) and Ibn Abbas (may Allah be pleased with them both).
It is also reported from the Companions that Abdullah bin Mas'ud (may Allah be pleased with him), al-Bara' bin Azib (may Allah be pleased with him), Abu Hurayrah (may Allah be pleased with him) and Uqbah bin Amir (may Allah be pleased with him) said four takbirs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6952