Sahih Al Bukhari Hadith Number 1333

Narrated Abu Huraira: Allah’s Messenger (peace be upon him) informed about the news of the death of An-Najash on the day he died. He went out with us to the Musalla and we aligned in rows and he said four Takbirs for An-Najashi’s funeral prayer.

23  Funerals (Al-Janaa’iz)
Hadith number 1333
Volume no 2
Chapter: 64 (There are four Takbir’s in the funeral prayers)