In the Qur’an we read in one Ayah

{يَدْخُلُونَ فِى دِينِ ٱللَّـهِ أَفْوَاجًا}

“They are entering God’s religion in throngs,”([1])

and elsewhere we read, that when those who were claiming to have faith and believed, the Qur’an states they should not be saying we believe, rather, but rather we surrender

 {وَلَمَّا يَدْخُلِ ٱلْإِيمَـٰنُ فِى قُلُوبِكُمْ}

for belief has not yet entered your hearts([2]).

Yes, belonging to a religion has stages: Warm stages, cool stages and cooked stages.  Every hot stage can become cold again and every cold stage may become hot again.  However, never will anything cooked become raw again.

Entry of people in to a religion is easy, and one that says “I witness that there is no God but Allahﷻ  and that Muhammad PBUH is the Messenger of Allahﷻ ” (Twin Declaration of Faith) becomes a Muslim. This stage is the becoming warm stage.  However, higher levels than that is to heat up to being very hot.  The companions of the Prophet, blessings be upon him and his Purified Household, with strong and overflowing feelings towards Islam, went to wars and were prepared to sacrifice their souls for the cause. However, the Qur’an speaks with them directly and asks them to pay a portion of the spoils of war:

{وَٱعْلَمُوٓا أَنَّمَا غَنِمْتُم مِّن شَىْءٍ فَأَنَّ لِلَّـهِ خُمُسَهُۥ وَلِلرَّسُولِ وَلِذِى ٱلْقُرْبَىٰ وَٱلْيَتَـٰمَىٰ وَٱلْمَسَـٰكِينِ وَٱبْنِ ٱلسَّبِيلِ إِن كُنتُمْ ءَامَنتُم بِٱللَّـهِ}

“Know that, whatever booty you take, the fifth of it is God’s, and the Messenger’s, … if you believe in God…”([3]).

Yes, it is possible for someone to say the Twin Declaration of Faith and even fight alongside the Prophet blessings be upon him and his Purified Household, but when it comes to wealth, they fall short and look the other way.  For this reason, the Qur’an makes it clear that along with the Twin Declaration of Faith and joining the wars and prayers, the rights of Allahﷻ and the Prophet, blessings be upon him and his Purified Household, and the poor must also be paid by believers. Only after we accept all responsibilities does faith truly enter our hearts and it is only for a niche group of people that Allahﷻ identifies as the Faithful Believers

{أُولَـٰٓئِكَ هُمُ ٱلْمُؤْمِنُونَ حَقًّا}

“those in truth are the believers”.([4])

The real faithful believers are a special set of people, as for those who are hypocrites and only outwardly show their faith, the Qur’an states

{وَمِنَ ٱلنَّاسِ مَن يَقُولُ ءَامَنَّا بِٱللَّـهِ وَبِٱلْيَوْمِ ٱلْـَٔاخِرِ وَمَا هُم بِمُؤْمِنِينَ}

“And some men there are who say, ‘We believe in God and the Last Day’; but they are not believers.” ([5])

[1] Al Nasr 110:2

[2] Al Hujjarat 49:14

[3] Al Anfal 8:41

[4] Al Anfal 8:4

[5] Baqarah 2:8