Nay, but they have denied the truth (this Qurān) when it has come to them, so they are in a confused state (can not differentiate between right and wrong). Sura Qāf: 5
Shaykh Uthaymīn:
“Likewise every person who rejects the truth the first time, then he should know that he will be trialed with doubts and uncertainty in accepting the truth in the future. Therefore it is obligatory upon us when we hear that this thing is the truth, that we say: “we hear and obey.”
Has everyone disbelieved who curses the religion or rejects the sunnah?
He answered hafidahullah:
There is no doubt whatsoever in this; whoever curses the religion or rejects the Sunnah then verily he has disbelieved, because he is a denier and disbeliever in the Sunnah; also he who curses Allah’s religion, which Allah has chosen for his slaves; then he has cursed that which Allah has chosen for his slaves and legislated for them, so this one has cursed Allah -azza wa jal- there is no doubt at all of his disbelief , he who belittles Allah (and attributes deficiencies to him; Glorified and far removed is Allah from all imperfections) .
Please note that declaring a specific individual to have disbelieved and left the fold of Islaam is an affair that is to be returned back to the Scholars and it is not for other than them to declare a specific individual to have disbelieved.
In The Name of Allaah, The Most Merciful The Bestower of Mercy
Question to Shaikh Saaleh Al-Fawzaan [may Allaah preserve him]: ”Some of the people claim that the manhaj of Ahlus Sunnah Wal Jamaa’ah is not suitable for this time, and they sight (as proof for their argument) that the precise regulations of the Sharee’ah held by Ahlus Sunnah cannot be actualized in this present era.
Answer:
The one who holds that the manhaj of the Salafus Saalih is not suitable for the rectification of the (affairs) in this time is one to be considered misguided and misguiding others because the manhaj of the Salafus Saalih is what Allaah has commanded us to follow till the establishment of the hour. He (sallal-laahu-alayhi-wasallam) said: ”’Verily those of you who live long after me will see a lot of differences, so hold fast to my Sunnah and the Sunnah of the Rightly-Guided Khulafaah after me. Cling to it tightly and bite unto it with your molar teeth”
This is an address to the ummah till the establishment of the hour. It demonstrates that the Manhaj of the Salaf must be followed and that it is suitable for rectifying the (affairs) in every time and place. Allaah (subhaanah) said:
‘And the first to embrace Islaam of the Muhaajroon (those who migrated from Makkah to Al-Madinah) and the Ansaar (the citizens of Al-Madinah who helped and gave aid to the Muhaajiroon) and also those who followed them exactly (in Faith). Allaah is well-pleased with them as they are well-pleased with Him.”
[وَٱلَّذِينَ ٱتَّبَعُوهُم بِـإِحۡسَـٰنٍ۬ -And also those who followed them exactly (in faith)]: this includes the entire ummah till the establishment of the hour. Therefore, it is obligatory upon the ummah to follow the manhaj of the Muhaajiroon and the Ansaar. Imaam Maalik (rahimahullaah) said: ‘The later part of this ummah will not be rectified except by that which rectified its earlier part.’
The one who wishes to isolate the ummah from the Salafus Saalih is one who wishes evil for the Muslims. He is one who wishes to change Islaam and he is one who wishes to initiate innovations and Mukhaalafaat (things that are in opposition to the pure Religion). It is obligatory to reject this one, cut off his argument and warn against his evil because the Manhaj of the Salaf must be followed and the Salaf must be taken as examples. The Manhaj of the Salaf must be followed and that is what is in the Book of Allaah and in the Sunnah of His Messenger as we have mentioned. The one who wishes to cut off the Khalaf of the Ummah from its Salaf is one who works corruption in the earth. It is obligatory to reject, refute his statement and warn against him. The shee’ah and those in agreement with them are the ones known for uttering such statements, so they are not be to be given any consideration.
[Source: Al-Muntaqaa Min Fataawaa Ash-Shaikh Saaleh Al Fawzaan: page:11-12]