Sultanul Awliya Shaykh Abdullah Faiz Dagestani (q.s) redefines a believer and unbeliever:
The 39th Grandshaykh of the Naqshabandi-Haqqani (Osmanli Naksibendi Way) teach us the meaning of believer and unbeliever according to Tasawwuf (Sufism).
In a shocking blow on literalists and mauturidi theologians, Grandshaykh declares that everyone who say: “Allah, God, Bhagavan/Adonai, Hallelujah” in their own language or tradition should be considered as a “believer”.
We would like to know, what’s the fatwa of British Sunni Imams against Shaykh Abdullah Dagestani (q.s) for making such a anti-sunni anti-maturidi heretical claim?
Mr Lokman Effendi, its time to book another flight to the U.K to come hug and lick the boots of external sunni scholars of U.K and elsewhere.

Lets wait and see for the Luton Imams to organise a meeting and to summon their demon Mr Lokman Effendi and demand Lokman to reject the teachings of Hazret Shaykh Abdullah Dagestani (q.s), just as they had done against the teachings of Hazret ibn Arabi (q.s) and other early Saints.
In the Book Mercy Oceans, we read in OPage 157-158
Who is an unbeliever?
Our Grandsheikh says whoever is never saying «Allah» is a kâfir, unbeliever. Anyone saying «Allah», even in his own language, you must not say to him «Kafir». This is clear, our Grandsheikh is leaving this so wide, so open, not making conditions, all Prophets just came to make people, believing in their Lord, not in themselves. Anyone saying «God» must be considered a believer. Even if a person says, as we do in English, «Oh my God», Allah is catching him. This is gigantic good news. The Prophet, peace be upon him, says if a person says: «Ya Rabb», Allah says to him: «I am here, oh my servant, what do you need?» Allah is closer to you than you to yourself.
Reference: Mercy Oceans, Page 157-158
These teachings goes against the narratives in Fiqh and Aqeedha (Jurisprudence and Theology) of traditional sunni and salafi Islam.
According to Quran, only those who believed in the Prophet Muhammad (a.s) is considered as believers.
Quran 2:4 and who believe in what has been revealed to you ˹O Prophet˺1 and what was revealed before you, and have sure faith in the Hereafter.
According to Quran and Hadiths, Prayer and Zakat together constitutes the definition of a believer:
Narrated Abdullah bin Buraidah narrated from his father:
that the Messenger of Allah (ﷺ) said: “The covenant between us and them is the Salat, so whoever abandons it he has committed disbelief.” Tirmidhi 2621 (sahih)
During the Caliphate of Hazret Abu Bakkar (ra), he wage war against those Muslims who refused to pay Zakat.
According to standard Sunni theology, one has to believe in five pillars of Islam and six pillars of Iman (faith) to be considered a believer. (Quran 2:285, Hadith2/40 hadith Nawawi).
This means, Jews, Christians, Hindus and even other people should be considered as believers. Especially we notice that external scholars like Zakir Naik, Ahmad Deedat (Sunni) and other quotes Hindu scriptures and explains that Prophet (a.s) is mentioned in the Hindu scriptures as the Kalki or final incarnation of the Lord Vishnu.
So many Hindus have converyed to Islam, realising that Prophet Muhammad (a.s) is the incarnation of their God, Lord Vishnu.
Our question to Zakir Naik and others is that: if a person come to Islam based on the description given in the books of their former religion, will their faith be considered authentic accoridng to Islamic aqeedha?.
Summary:
Sufism (Islamic spirituality( is the universal religion of the Prophets and Saints, it is never excluding others from the previous scriptures and covenants. But the way of Shariah and Aqeedha (Islamic law and theology) excludes people of different scriptures and backgrounds. Although some verses in the Quran and Hadiths uphold universality of religious way.