Al-Shaybani narrates from al-Sha'bi (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) came to a fresh grave and offered the funeral prayer over it, and the Companions (may Allah be pleased with them) also prayed behind him (peace and blessings be upon him), and he (peace and blessings be upon him) said four takbirs. I said to Amir: Who narrated this hadith to you? He said: A trustworthy narrator, from Abdullah bin Abbas (may Allah be pleased with them both).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 7002