For purification of the self, it is inevitable to get rid of suspicion as it arouses in the inward of a man. When one mistrusts then it is hidden in the inward. The other person is clueless when one is suspicious of him. This is illness and it is not new. In sura Fath, Allah says:

وَ ظَنَنۡتُمۡ ظَنَّ السَّوۡءِ ۚۖ وَ کُنۡتُمۡ قَوۡمًۢا بُوۡرًا

Meaning: And you imagined a highly evil speculation and became a people bound to perish. (Quran 48:12)

It is in sura al-Hujurat:

یٰۤاَیُّہَا الَّذِیۡنَ اٰمَنُوا اجۡتَنِبُوۡا کَثِیۡرًا مِّنَ الظَّنِّ ۫ اِنَّ بَعۡضَ الظَّنِّ اِثۡمٌ

Meaning: O believers! Shun such suspicion; for some suspicion is a sin. (Quran 49:12)

The Holy Prophet said, “Protect yourself from suspicion as nothing is more baseless than it.” (Hadith)

It is a baseless accusation. Its seeds are sowed in the inward. One has become suspicious of a man standing in front of him. The first step is that one becomes suspicious, the second step is that one distances from the other person and lastly one breaks relationship with them.

What is the extreme case of suspicion? To mistrust the perfect spiritual guide. Satan attacks a disciple by sowing the seeds of mistrust in his inward about the spiritual guide. It is a spiritual ailment and it requires purification. If one has evidence against the other person then he should opt for some other method instead of mistrusting. Mistrusting has a huge role in breaking relations. Even in families, there are elements of mistrust often caused by a backbiter. What a backbiter does? He hears something, adds to it and tells you the corrupted version. What the actual words were? What was the intention of the speaker? Why he said it? What was his purpose? The backbiter would not disclose any of it. For example, I say that Naeem is a sharp person. What I actually meant was that he is an intelligent man. A backbiter will go and tell Naeem that I was calling him shrewd. This will create mistrust in Naeem’s inward. It has been advised to not mistrust. In the book ‘Sufism-the Soul of Islam’, this spiritual ailment is also discussed in detail. A person repents on committing a sin but mistrusting is such a sin that one does not feel the need to repent. One always claims that he has done the right thing. A person repents of the sins committed out of lust of self as he remembers them but does not repent of the sins committed out of different spiritual ailments. One even dies with these sins. These are such sins from which purification of the self is must.

  The Holy Quran states:

قَدۡ اَفۡلَحَ مَنۡ زَکّٰىہَا

Meaning: Indeed, the one who purifies his (inciting) self succeeds. (Quran 91:9)

Purification means to take out all these things from the inward. If these idols are in the inward, a man cannot recognize Allah. What is meant by the purification of the self? To get rid of these spiritual ailments as is written in the book ‘Sufism-The Soul of Islam’. When one gets rid of these ailments, he is purified and who is the friend of a purified man – Allah Almighty.