‏الصلاة : Hadeeth No:2122 Abu Marthad al-Ghanawi reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: Do not pray facing towards the graves, and do not sit on them....

‏الصلاة : Hadeeth No:869 This hadith is narrated by Ibn Uyaina with the same chain of transmitters....