وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَلِيَّ بْنَ أَبِي طَالِبٍ، كَانَ يَتَوَسَّدُ الْقُبُورَ وَيَضْطَجِعُ عَلَيْهَا ‏.‏ قَالَ مَالِكٌ وَإِنَّمَا نُهِيَ عَنِ الْقُعُودِ عَلَى الْقُبُورِ فِيمَا نُرَى لِلْمَذَاهِبِ ‏.‏

ahya related to me from Malik that he had heard that AIi ibn AbiTalib used to rest his head on graves and lie on them. Maliksaid, "As far as we can see ,it is only forbidden to sit on graves torelieve oneself." Translation Not Available

Book Ref: Muwatta Imam Malik Book 16 Hadith 556
Web Ref:  Muwatta Imam Malik Book 16 Hadith 34