Grave of claimed Wali neither benefits nor harms
27-6-2016 | IslamWeb
Question:
Assalaamu alaykum. A man had four sons; three of them became medical doctors, and the remaining one developed some kind of mental disease. People say that he was a bright student and was even better than his brothers. As the development of mental disease was an unpredictable event, some people assumed that he became mad because he used to hunt pigeons and once hunt a pigeon on a tree near the grave of Baba (a supposed wali [saint]). They argue that this was the cause of his madness. I want to ask whether it could be a case of magic? Someone might have done it out of jealously of his outstanding performances in his studies. Or it could be a case of jinn possesion? If that turned out to be the case, then what could I do to cure him? May Allaah reward you.
Answer:
All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad 
is His slave and Messenger.
If there is no apparent reason for what happened to him and it is believed that he was most likely affected by magic, jinn possession, or an evil eye, then he should be treated with Ruqyah (healing through Quranic reading and supplications). Please refer to fataawa 82918 and 88660 about treatment with Ruqyah.
As for linking his condition to the hunting of a pigeon on a tree near the grave of a man who is claimed to be a Wali of Allaah, then this is one of the ways that the devil uses to corrupt people's beliefs, as is the case with some ignorant Muslims who believe that the dead in the graves have the power to benefit or harm them. Such a corrupt belief could lead the Muslim into committing Shirk (polytheism).
Ibn Al-Qayyim 
wrote:
"Our Shaykh (Ibn Taymiyyah) said, 'This is the reason why the Islamic sharee'ah forbids building mosques over graves, which is the very action that had lured the past nations into Shirk, both major and minor Shirk. Indeed, people's hearts were attached to the statues of their pious ancestors and other statues which they claimed to be a form of zodiac signs of the planets and the like. Moreover, the hearts are more inclined towards committing acts of Shirk over the grave of a man who is believed to be pious compared to a statue made of wood or stone. This is why we see the people of Shirk displaying remarkable signs of submission and devotion at those graves, and they worship them in their hearts in a way that they do not do in the houses of Allaah (mosques) or at the time before dawn (which is a very blessed time for worship)..." [Ighaathat Al-Lahfaan]
Allaah knows best.