Sahih Bukhari Volume 2, Book 23, Hadith Number 468.
The man went to pick it up and by the time he returned to him, the crushed head had returned to its normal state and the man came back and struck him again (and so on). I said, ‘Who is this?’ They told me to proceed on; so we proceeded on and passed by a hole like an oven; with a narrow top and wide bottom, and the fire was kindling underneath that hole. Whenever the fire-flame went up, the people were lifted up to such an extent that they about to get out of it, and whenever the fire got quieter, the people went down into it, and there were naked men and women in it. I said, ‘Who is this?’ They told me to proceed on. So we proceeded on till we reached a river of blood and a man was in it, and another man was standing at its bank with stones in front of him, facing the man standing in the river. Whenever the man in the river wanted to come out, the other one threw a stone in his mouth and caused him to retreat to his original position; and so whenever he wanted to come out the other would throw a stone in his mouth, and he would retreat to his original position. I asked, ‘What is this?’ They told me to proceed on and we did so till we reached a well-flourished green garden having a huge tree and near its root was sitting an old man with some children. (I saw) Another man near the tree with fire in front of him and he was kindling it up. Then they (i.e. my two companions) made me climb up the tree and made me enter a house, better than which I have ever seen. In it were some old men and young men, women and children.
Then they took me out of this house and made me climb up the tree and made me enter another house that was better and superior (to the first) containing old and young people. I said to them (i.e. my two companions), ‘You have made me ramble all the night. Tell me all about that I have seen.’ They said, ‘Yes. As for the one whose cheek you saw being torn away, he was a liar and he used to tell lies, and the people would report those lies on his authority till they spread all over the world. So, he will be punished like that till the Day of Resurrection.
The one whose head you saw being crushed is the one whom Allah had given the knowledge of Quran (i.e. knowing it by heart) but he used to sleep at night (i.e. he did not recite it then) and did not use to act upon it (i.e. upon its orders etc.) by day; and so this punishment will go on till the Day of Resurrection. And those you saw in the hole (like oven) were adulterers (those men and women who commit illegal sexual intercourse). And those you saw in the river of blood were those dealing in Riba (usury). And the old man who was sitting at the base of the tree was Abraham and the little children around him were the offspring of the people. And the one who was kindling the fire was Malik, the gate-keeper of the Hell-fire. And the first house in which you have gone was the house of the common believers, and the second house was of the martyrs. I am Gabriel and this is Michael. Raise your head.’ I raised my head and saw a thing like a cloud over me. They said, ‘That is your place.’ I said, ‘Let me enter my place.’ They said, ‘You still have some life which you have not yet completed, and when you complete (that remaining portion of your life) you will then enter your place.'”