What is the ruling on someone who does not declare the disbelievers as non-Muslims?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The Jews, the Christians, the Buddhists and other people who follow a religion other than Islam are all non-Muslims, and this is something which is known in Islam by absolute evidences and which on one can deny. Therefore, whoever denies that they are non-Muslims, or doubts their disbelief or does not declare them as non-Muslims, then he is a non-Muslims. That is because it is one of the nullifiers of Islam not to declare the disbelievers as non-Muslims, or doubts their disbelief. Al-Qaadhi 'Iyaadh when stating the things that are agreed by the consensus of the scholars to be a disbelief, said: 'It is for this reason that we consider all the people who follow a religion other than Islam as non-Muslim even if such person practices Islam and believes n it, and believes that all other beliefs are void, because he showed other than what he believes in.'

One of the Hanbali Books reads: '…Or that he does not declare the people who follow a religion other than Islam as non-Muslims, like the Christians and the Jews, or that he doubts their disbelief, or that he declares their faith as correct, then he is a non-Muslim as he denies the saying of Allaah (which means): {And whoever desires other than Islam as religion, never will it be accepted from him, and he, in the Hereafter, will be among the losers.}[Quran 3:85].'

Allaah Knows best.