Sahih Al Bukhari Hadith Number 1240

Narrated Abu Huraira: I heard Allah’s Messenger (peace be upon him) saying, “The rights of a Muslim on the Muslims are five: to respond to the salaam, visiting the sick, to follow the funeral processions, to accept an invitation, and to reply to those who sneeze. (see Hadith 1239)

23  Funerals (Al-Janaa’iz)
Hadith number 1240
Volume no 2
Chapter: 2 (The order of following the funeral procession)