When Imam Al Sadiq peace be upon him was asked about the Sufis, he said: “They are our enemies. Whoever is inclined to them is of them and will be gathered with them on Judgement Day. There will be people who claim that they love us, but will be inclined to the Sufis, they will resemble them, they will use their titles; they will replicate their words. Whoever is inclined to them is not of us. We reject those ones; whoever denies them and responds to their words will be granted the status of performing Jihad with the prophet peace be upon him and his family” Safinat Al Bihar by Al Qumi vol 2, page 57.
Imam Al Ridha peace be upon him said: “Whoever is mentioned before him the Sufis and he did not deny them by speech or in private does not become of us. Whoever rejects them will be granted the status of performing Jihad with the prophet peace be upon him and his family”, same previous reference.
Imam Al Askari peace be upon him said to Abi Hashim Al Jaffari: “Oh Abi Hisham! There will time when people seem to be happy, but their hearts are full of distress. The true Sunna among them is described as an innovation; an innovation among them is called a Sunna. A true believer among them is humiliated; a known Libertine among them is highly respected. The ones who rule them are tyrants. Their scholars do walk towards the gates of darkness. The wealthy people among them steal from their poor ones. The young ones are more esteemed than the elderly. Any ignorant will be taken as an expert scholar. People will not be able to distinguish between the faithful and unfaithful. People will not be able to distinguish between human wolves and human sheep. Their scholars are the worst of Allah’s creation ever because they are inclined towards Philosophy and Sufism. By Allah! Those are the ones who bring aggression and corruption into Islam. They take our Shia astray. If they secure a high position, they will not get enough from corruption; if they do not, they will acts of worship are nothing but pretence. They are the bandits on the ways of the believers. They are the ones who call for the path of the disbelievers. Beware them! Keep your faith secure from them! Safeguard your faith from them! Oh Abi Hashim! This had been told to me by my forefathers, so keep what I told you safe and reveal it appropriately”.
Ref: Safinat Al Bihar by Al Qumi vol 2 page 58.