Sahih Muslim Book 40, Hadith Number 6862.
Anas b. Malik reported Allah’s Apostle (may peace be upon him) having said: When the servant is placed in his grave and his companions retrace their steps arid he hears the noise of the footsteps, then two angels come to him and make him sit and say to him: What you have to say about this person (the Holy Prophet)? If he is d believer, lie would say: I bear testimony to the fact that he is a servant of Allah and His Messenger. Then it would be said to him: Look to your seat in the Hell Fire, for Allah has substituted (the seat of yours) with a seat in Paradise. Allah’s Messenger (may peace be upon him) said: He would be shown both the seats. Qatada said: It was mentioned to us that his grave (the grave of a believer) expands to seventy cubits and is full with verdure until the Day when they would be resurrected.