https://abukhadeejah.com/decisive-proofs-against-the-sufis-who-take-graves-as-places-of-worship-the-condemnation-of-the-one-who-worships-allah-at-the-grave-of-a-righteous-man-so-how-much-worse-is-the-one-who-actually-worsh/
Chapter 20: Those who worship Allāh at the graves of righteous men, and those who ask the dead for help, and the Green Dome over the Prophet's Mosque and his grave. Kitāb At-Tawheed.