All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The Deobandi movement is a sect among the Muslims that originated in India. It was established to spread the teachings of Islam, preserve the Islamic identity, combat foreign ideas that infiltrated into the Muslims, and spread the Arabic language.
However, like many other Muslim sects, this sect is not free from deviant beliefs, ideologies and practices.
The Deobandis adopt the Maaturidi beliefs and some Sufi methods, such as Qaadiriyyah and Naqshbandiyah. They are fanatic to the Hanafi School of jurisprudence.
The Mu’tazilah, as well, are a group that is affiliated with Islam, and they have many deviant ideas. They say that the Quran is created and they deny seeing Allah in the Hereafter. They do not believe in divine decree (they claim that the actions of man are not due to divine decree) and are of the view that a person who commits a major sin will enter Hellfire eternally, and they have other such dangerous ideas.
The scholars differed regarding declaring the Mu'tazilah as non-Muslims; some of them are of the view that they are Muslims because they are included in the term of the “Muslim nation” in the Hadeeth of the Prophet that reads: “My (Muslim) nation will split into 73 sects.” [Al-Bayhaqi, Al-Haakim and others] Attributing the sects to the Muslim nation indicates that they are Muslims [and not disbelievers].
It should be noted that if a Muslim does an act of disbelief, whether it is a saying or an action, he is not ruled to be a disbeliever unless after all the conditions of disbelief are met. For more benefit on these conditions, please refer to Fataawa 8106 and 87963.
Allah knows best.