Salam,
The Wahhabis of Saudi Arabia mission was mainly against Sufism. They are also known to many as Salafis, those who follow on the footsteps of the salaf.
Islam has two main dimensions from the One Almighty. Allah says that He is the First and the Last. The Manifest and the Hidden. Thus, even the Qur'an speaks of itself as a Hidden Book in Sura al-Waqi'a:
56:75 Furthermore I call to witness the setting of the Stars (the manifest),-
56:76 And that is indeed a mighty adjuration if ye but knew,-
56:77 That this is indeed a Qur'an Most Honourable,
56:78 In a Hidden Book
56:79 Which none shall touch but those who are pure.
Now comes to the question, if the Qur'an we find in books describes itself that it is hidden, then what is the Qur'an? How can what we see tell us that it is hidden?
This is where the Sufis come from. To them the outer garments of religion are symbols to the mystical inner truth, that none can unfold, except those who are Pure. Hence, one of the root words for Sufi is "safa'a" which means purity. Inner purity.
Now, Wahhabis or Salafis are not to blame, however, when misunderstandings may arise. They are known to be literalists. Literalists cannot see the inner or hidden part of the religion. They do not see symbols, they just see what is there and take it as is. Of course, Allah describes Himself as the Manifest and the Hidden, so we cannot say they are wrong, but maybe not complete, due to ignorance from the side of some Wahhabis.
However, that does not make Sufis not as ignorant either. The main issues that Wahhabis (Salafis) have against Sufism are those things that may lead to "shirk". This includes venerating saints (awliya') and asking them for help. Wahhabis take the point of view that only Allah should be prayed for, because praying for any other would lead to "shirk" (renouncing the Omnipotent Unity of Allah) and believing that a creature may provide better than Providence (ar-Razzaq) Himself. Although to the Sufi elite, symbols are known to be mere symbols, to the majority of the public, those symbols are actually worshipped and therefore fall into their own ignorance.
Of course asking a saint for help is not wrong, but the fact may lead to "shirk" and this is what Wahhabis do not like. For even in the Qur'an, the sons of Jacob (pbuh) ask their father Jacob for forgiveness, and in reply he says that he will seek Allah's forgiveness for them.
In Sufis case, sufis are vulnerable of putting trust on a saint instead of Allah. However, that is due to the ignorance of some sufis.
The Sufi Ibrahim ibn al-Khawwas (d. 904) is quoted as saying that the "Initiator of Saints" Sayyidna Khidr (pbuh) offered to accompany him but Khawwas refused, fearing that in Khidr's company he would put his trust in Khidr instead of in God.
Therefore, to some extent the Wahhabis have a point, and to another extent the Sufis also have a point.
Now as to what is right and what is wrong, maybe it is best not to trust either the words of a Wahhabi nor a Sufi, but to trust in Allah, as the Wahhabis say. For those who seek to know the Truth for the love of the Truth sincerely from all their heart and all their soul, Allah will not leave them misguided, for Allah is the Truth, as the Sufis say.
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