Q: What should I do if I see someone calling upon a dead person at his gravesite, seeking his help — someone committing an outright act of shirk. When calling him to worship Allāh alone, do I advise him as a Muslim, or should I consider him a Polytheist?

A: Invite him using a different approach, not this way or that way. Say to him, “O Fulān! O ʿAbdullāh! This thing you are doing is a kind of shirk, and it is not (the correct way of) worship! It is the way of the Pagans from Jāhiliyyah (the pre-Islamic period of ignorance)! It is the way of (the Pagans of) Quraysh and those like them!”

This is because there may be reasons he should not be declared outside of Islām in this case, and declaring him outside of Islām would run him away as soon as you speak to him!

Declaring someone outside of Islām is based on more than just an action of shirk. The action may be shirk, but the one doing may not be a Mushrik (Polytheist), since there could be something preventing us from making takfīr (declaring him a disbeliever), like ignorance or not understanding firmly what the scholars say (about his action).

Also, to address him as a Polytheist would run him away. So call him by his name, and explain to him clearly that what he is doing is shirk.

Source: Al-Fawāʾid al-ʿIlmiyyah min al-Durūs al-Bāziyyah (2/273), Al-Risālāh printing, 1430, as quoted by Shaykh Aḥmad Zahrānī
Translated by: Mūsá Richardson (1431/8/28)