Sayyiduna Abu Umamah bin Sahl bin Hunayf (may Allah be pleased with him) said that men from among the Companions of the Messenger of Allah (peace and blessings be upon him) informed him that in the funeral prayer the imam should say takbir, then send blessings upon the Prophet (peace and blessings be upon him), and make purely sincere supplication in the three takbirs, then give a light salam when he finishes; and the Sunnah is that those behind him do just as their imam did.
Al-Zuhri said: Abu Umamah narrated that to me while Ibn al-Musayyib was listening, and he did not object to it.
Ibn Shihab (may Allah have mercy on him) said: I mentioned to Muhammad bin Suwayd (may Allah have mercy on him) what Abu Umamah (may Allah be pleased with him) had informed me of the Sunnah in the prayer over the deceased, and he said: I heard al-Dahhak bin Qays (may Allah be pleased with him) narrating from Habib bin Maslamah (may Allah be pleased with him) about a funeral prayer he offered, the same as what Abu Umamah (may Allah be pleased with him) narrated.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6962
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he asked Sayyiduna Ubadah bin al-Samit (may Allah be pleased with him) about the funeral prayer, and he said: By Allah! I will tell you: you begin by saying takbir, then you send blessings upon the Prophet (peace and blessings be upon him), and you say: 'Allahumma inna abdaka fulanan kana la yushriku bika shay'an wa anta a'lamu bihi, in kana muhsinan fazid fi ihsanihi, wa in kana musi'an fatajawaz anhu, Allahumma la tahrimna ajrahu wa la tudillana ba'dahu' (O Allah, this servant of Yours, so-and-so, did not associate anything with You, and You know him best. If he was a doer of good, then increase his good; and if he was a wrongdoer, then overlook his faults. O Allah, do not deprive us of his reward, and do not lead us astray after him.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6963