The Book of Prayers (Kitab Al-Salat) 
Muslim :: Book 4 : Hadith 2121
Abu Marthad al-Ghanawi reported Allah's Messenger (may peace be upon him) as saying: Do not sit on the graves and do not pray facing towards them.
The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 2121
Abu Marthad al-Ghanawi reported Allah's Messenger (may peace be upon him) as saying: Do not sit on the graves and do not pray facing towards them.