What is Fusooq—Shaikh Fawzaan (may Allaah preserve him) explains…
Concerning the statement of Allaah (The Most High): [وَكَرَّهَ إِلَيْكُمُ الْكُفْرَ وَالْفُسُوقَ وَالْعِصْيَان] – ”And has made disbelief, wickedness and disobedience (to Allah and His Messenger) hateful to you.” [Al-Hujuraat. Ayah 7] Al-Fusooq and Al-Faasiqoon have been mentioned several times in the Qur’aan and the Sunnah, so what is Fusooq and how can a Muslim be careful of becoming from a people who are Faasiqeen?
Concerning Allaah’s (The Most High) statement: [وَكَرَّهَ إِلَيْكُمُ الْكُفْرَ وَالْفُسُوقَ وَالْعِصْيَان]- ”And has made disbelief, wickedness and disobedience (to Allah and His Messenger) hateful to you”; He (Glorified Be He) mentioned the three types of acts of disobedience in this noble Ayah:
(A) The type of disobedience that removes a person from the fold of Islaam, such as Kufr (Akbar) and Shirk (Akbar). [Ref 1]
(B) The major type of disobedience which is lesser than Kufr (Akbar) and Shirk (Akbar) and it does not remove a person from the Religion but it decreases one’s Imaan—a manifest decrease–; such as fornication, theft, drinking alcohol and other than that of the major sins. They are referred to as Fusooq (wicked deeds) and the person who commits them is referred to as a Faasiq (wicked sinner) because Fisq means removing oneself from obedience to Allaah (The Mighty and Majestic].
(C) Then He (The Most High) mentioned the type of disobedience that is lesser than the major sins and are not tantamount to Fisq, and they are the minor sins.
So Allaah (Glorified Be He) informed (us) that He has made all these three types of disobedience hateful to the people of Imaan and make them have a love for the various types of acts of obedience and righteous actions that draws them close to their Lord.
[Source: Al-Muntaqaa Min Fataawaa Fadeelatish Shaikh Saaleh Al-Fawzaan Vol 1 page 244. Fatwa Number 142]
[Ref 1] NB: To declare that a Muslim has left the fold of Islaam is the responsibility of the rightly guided scholars and not other than them. Regarding the principles of Takfeer, visit link: http://www.salafipublications.com/sps/sp.cfm?secID=MNJ&subsecID=MNJ09&loadpage=displaysubsection.cfm