Invoking the dead and the absent like Prophets and Awliya’ (pious people)

Question 11: My father believes in the righteousness of a dead shaykh known as a Walee’ (a pious person). He makes Tawassul (supplicating to Allaah through a means) by this shaykh and associates him with Allaah in Du’aa (supplication), for example, he says: “O Allaah! O master Abdul-Salaam!” What is the ruling on this, taking into account that my father performs Salaah (Prayer), observes Sawm (Fast) and, pays Zakaah (obligatory charity)?

Answer: Making Du’aa to the dead and the absent like the Prophets, Awliya’ (pious people), and the like, whether alone or along with Allaah, is an act of Al-Shirk-ul-Akbar (major form of associating others in worship with Allaah), even if… read more here.