Hadith #3229 (Sunan Abi Dawud)
Book: Funerals (Kitab Al-Jana'iz)
Narrator(s): al-Aswad bin Shayban al-Sadusi الأسود بن شيبان السدوسي, Bashayr bin Nahayk بشير بن نهيك السدوسي, Sahl bin Bkar bin Bashr سهل بن بكار بن بشر
Grade: Sahih

The Messenger of Allah (ﷺ) as saying: Do not sit on the graves, and do not pray facing them.

Source: https://parallelquran.com/hadith/sunan-abi-dawud-3229/