Ibn Jurayj ابن جريج · The Book on Jana''iz (Funerals)

The Prophet said: "Do not sit on the graves nor perform Salat towards them."

"The Messenger of Allah passed by the graves of Al-Madinah, so he turned his face towards them and said: (As-Salamu alaikum ya ahlul-qubur! Yaghfirul-lahu lana wa lakun, antum salafuna wa nahnu bil-athar.) 'Peace be upon you O inhabitants of the grave! May Allah forgive us and you; you are our predecessors and we are to follow you.'"