Jami` at-Tirmidhi 1023
جامع الترمذي#1023SahihAbdur-Rahman bin Abi Laila said:"Zaid bin Arqam would say four Takbir for our funerals. (Once) he said five Takbir for a funeral so we asked him about that and he said: 'The Messenger of Allah would say those Takbir
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Muslim
In-book reference: 10:59