Sahih Bukhari Volume 2, Book 23, Hadith Number 452.

Narated By Ibn ‘Umar : The Prophet looked at the people of the well (the well in which the bodies of the pagans killed in the Battle of Badr were thrown) and said, “Have you found true what your Lord promised you?” Somebody said to him, “You are addressing dead people.” He replied, “You do not hear better than they but they cannot reply.”