Sahih Bukhari: Volume 2, Book 23, Number 472:

Narrated 'Aisha:

Allah's Apostle in his fatal illness said, "Allah cursed the Jews and the Christians, for they built the places of worship at the graves of their prophets." And if that had not been the case, then the Prophet's grave would have been made prominent before the people. So (the Prophet ) was afraid, or the people were afraid that his grave might be taken as a place for worship.

Sahih Bukhari: Volume 2, Book 23, Number 425:

Narrated 'Aisha:

When the Prophet became ill, some of his wives talked about a church which they had seen in Ethiopia and it was called Mariya. Um Salma and Um Habiba had been to Ethiopia, and both of them narrated its (the Church's) beauty and the pictures it contained. The Prophet raised his head and said, "Those are the people who, whenever a pious man dies amongst them, make a place of worship at his grave and then they make those pictures in it. Those are the worst creatures in the Sight of Allah."

Sahih Bukhari: Volume 1, Book 8, Number 426:

Narrated 'Aisha:

Um Salama told Allah's Apostle about a church which she had seen in Ethiopia and which was called Mariya. She told him about the pictures which she had seen in it. Allah's Apostle said, "If any righteous pious man dies amongst them, they would build a place of worship at his grave and make these pictures in it; they are the worst creatures in the sight of Allah."

Sahih Bukhari: Volume 2, Book 23, Number 414:

Narrated 'Urwa:

Aisha said, "The Prophet in his fatal illness said, 'Allah cursed the Jews and the Christians because they took the graves of their Prophets as places for praying."' Aisha added, "Had it not been for that the grave of the Prophet (p.b.u.h) would have been made prominent but I am afraid it might be taken (as a) place for praying.

Sahih Bukhari: Volume 1, Book 8, Number 428:

Narrated Abu Huraira:

Allah's Apostle said, "May Allah's curse be on the Jews for they built the places of worship at the graves of their Prophets."

Sunan Abu Dawud: Book 20, Number 3230:

Narrated Abdullah ibn Abbas:

The Apostle of Allah (peace_be_upon_him) cursed women who visit graves, those who built mosques over them and erected lamps (there).

Sunan Abu Dawud: Book 20, Number 3214:

Narrated Al-Qasim ibn Muhammad ibn AbuBakr:

I said to Aisha! Mother, show me the grave of the Apostle of Allah (peace_be_upon_him) and his two Companions (Allah be pleased with them). She showed me three graves which were neither high nor low, but were spread with soft red pebbles in an open space.

Sahih Muslim: Book 004, Number 1083:

Narrated Jundub ibn Abdullah (RAA):

I heard from the Apostle of Allah (SAW) five days before his death and he said: I stand acquitted before Allah that I took anyone of you as friend, for Allah has taken me as His friend, as he took Ibrahim as His friend. Had I taken any one of my Ummah as a friend, I would have taken AbuBakr as a friend. Beware of those who preceded you and used to take the graves of their prophets and righteous men as places of worship, but you must not take graves as mosques; I forbid you to do that.

Sahih Muslim: Book 004, Number 2116:

Jabir said:

Allah's Messenger (may peace be upon him) forbade that the graves should be plastered or they be used as sitting places (for the people), or a building should be built over them.

Sahih Muslim: Book 004, Number 2121:

Narrated Abu Marthad al-Ghanawi:

Allah's Messenger (may peace be upon him) said Do not sit on the graves and do not pray facing towards them.

Sahih Muslim: Book 004, Number 2118:

Jabir said that he was forbidden to build pucca graves.

Sahih Muslim: Book 004, Number 2114:

Thumama b. Shafayy reported:

When we were with Fadala b. 'Ubaid in the country of the Romans at a place (known as) Rudis, a friend of ours died. Fadala b. 'Ubaid ordered to prepare a grave for him and then it was levelled; and then he said: I heard the Messenger of Allah (may peace be upon him) commanding (us) to level the grave.

Sahih Muslim: Book 004, Number 2115:

Abu'l-Hayyaj al-Asadi told that 'Ali (b. Abu Talib) said to him:

Should I not send you on the same mission as Allah's Messenger (may peace be upon him) sent me? Do not leave an image without obliterating it, or a high grave without levelling It. This hadith has been reported by Habib with the same chain of transmitters and he said: (Do not leave) a picture without obliterating it.