Sahih Bukhari Volume 2, Book 23, Hadith Number 456.
Narated By Anas bin Malik : Allah’s Apostle said, “When (Allah’s) slave is put in his grave and his companions return and he even hears their footsteps, two angels come to him and make him sit and ask, ‘What did you use to say about this man (i.e. Muhammad)?’ The faithful Believer will say, ‘I testify that he is Allah’s slave and His Apostle.’ Then they will say to him, ‘Look at your place in the Hell Fire; Allah has given you a place in Paradise instead of it.’ So he will see both his places.” (Qatada said, “We were informed that his grave would be made spacious.” Then Qatada went back to the narration of Anas who said;) Whereas a hypocrite or a non-believer will be asked, “What did you use to say about this man.” He will reply, “I do not know; but I used to say what the people used to say.” So they will say to him, “Neither did you know nor did you take the guidance (by reciting the Quran).” Then he will be hit with iron hammers once, that he will send such a cry as everything near to him will hear, except Jinns and human beings. (See Hadith No. 422).