Wali ad din al Iraqi (d 826 h) was asked
مسألة: سئلت عمن يزور الصالحين من الموتى فيقول عند قبر الواحد منهم: (يا سيدي فلان أنا مستجير بك ، أو متوسل بك أن يحصل لي كذا وكذا، أو أطلب منك أن يحصل لي كذا وكذا) ، أو يقول: (يا رب أسألك بمنزلة هذا الرجل أو بسره أو بعمله أن يفعل لي كذا وكذا)، هل هذه العبارات حسنة أو غير حسنة، أو بعضها حسن وبعضها قبيح؟ وما كانت السلف تقول عند زيارة قبور الصالحين؟
That if a person visit a righteous among the dead and says : O sayyidi so and so, I am asking your help, or make him tawassul to get such and such or ask him help for such and such or say O Rabbi I ask you by the status of this man.. Are these statements good or not, or some of them are good and others are ugly.?
He replied:
It is allowed to visit the graves and the grave of righteous and it is also allowed to make dua to Allah near the graves as Allah accepted the duas near the grave of righteous Maruf al Karkhi, then he said about asking help from the dead righteous.
وأما قوله: (أنا أطلب منك أن يحصل لي كذا وكذا) فأمر منکر ، فالطلب إنما هو من الله تعالى، والتوسل إليه بالأعمال الصالحة أو بأصحابها أحياء وأمواتا لا ينكر
As for the saying (I ask/request you to get me such and such) this practice is MUNKAR because asking/requesting (Talab) is from Allah tala alone. And there is no inkar on tawassul of the righteous deeds (I.e. o Allah I ask you through so and so good deed) And the living or the dead righteous.
فتاوى ولي الدين العراقي (ص:١٦٦) ط/ دار الفتح.
See also
كتاب المجموع الثمين في حكم دعاء غير رب العالمين
[محمد بن عبد الله المقشي]
The muhaqqiq of this fatawa is extreme Sufi, who said Istigatha is allowed and went against al Iraqi’s fatwa.
Note: Dua to Allah near the graves, tawassul of righteous deeds and living being and tawassul of dead by saying O Allah i ask you by the tawassul of so and so righteous dead is not the topic. The topic is Istigatha through dead. Which is Munkar.