The Rifaa’is who stab themselves with knives but are not affected by it
Question

                What is your opinion of those who call themselves daraaweesh (pl. of darweesh or “dervish”) and stab themselves with knives, daggers, etc? Whilst they do that, before they say “Ya Allaah (O Allaah)”, they say, “Ya Rifaa’i (O Rifaa’i).” What is the shar’i view of this? Is there any evidence (daleel) for what they do? May Allaah reward you with good.
Praise be to Allah.They are liars and cheats. There is no basis for their actions. In 
          fact they are tricksters who use things to deceive the people so that 
          the people will think that they are stabbing themselves when that is 
          not really the case. It is a trick whereby they deceive the eye and 
          bewitch people. This is like what Allaah said about the sorcerers of 
          Pharaoh, that they were trying to frighten the people and that they 
          bewitched their eyes. The point is that it is not permissible to believe 
          in this kind of people – evildoers and deceivers – who have no basis 
          for what they do. They are liars and tricksters who deceive people. 
          When they call upon al-Rifaa’i, or anybody else, this is shirk akbar 
          (major shirk), as is the 
          case of one who says “O Rifaa’i” or “O Messenger of Allaah, grant us 
          victory: or “intercede for us” or “O ‘Ali” or “O Seedi” or “O Husayn” 
          or “Ya Seedi al-Badawi” and so on. All of that is shirk 
          akbar and it is all worship of people or things other than 
          Allaah. All of that is like the actions of those who worship graves, 
          and those who worshipped al-Laat and al-‘Uzza and their ilk. It is shirk akbar – we seek refuge in Allaah from that. When these 
          people stab themselves with daggers and knives, it is trickery and deception 
          which has no basis; by doing this they are liars and evildoers. The 
          authorities – if there are Muslim rulers in their countries – have to 
          put a stop to this, and they must punish them and discipline them until 
          they repent from their evil actions.