BENEFIT IN AQEEDA/BELIEF
Sheikh Saleh Al-Fawzan may Allāh preserve him stated that:
Whosoever believes that the dead can benefit or harm and he takes vow to them and get close to them(by giving them act of worship) he is a Mushrik (a polytheist ) and have committed a major shirk that takes one out of Islam.
{ Al-muntaqah 83/1 }
Translation: Knowledge and Action