Surah 20 v 100 Whoever turns away from it (this Qur'an - i.e. does not believe in it, nor acts on its orders), verily, they will bear a heavy burden (of sins) on the Day of Resurrection,
101 They will abide in that (state in the Fire of Hell) - and evil indeed will it be that load for them on the Day of Resurrection;
WHO IS A MUSLIM ?
WHO OBEY ALLAH AND FOLLOW HIS LAST MESSENGER IS A MUSLIM,.....BY NAME NONE WILL BE MUSLIM ,ONE BECOMES MUSLIM BY DEEDS
WHO DO NOT KNOW WHAT QURAN SAYS NOR FOLLOW IT CANT BE A MUSLIM,
WHO FUNCTION ACCORDING QURAN IS A MUSLIM .............
The munafiqs, those who reject Faith after accepting Islam, do not aim to earn the good pleasure of Allah SWT like the believers, even when they live among them. Having quite different a personality than the believers, the munafiqs keep company of the believers sometimes to acquire material gain, and sometimes to plot against the believers - just because of their grudge against them. Their belief in Allah SWT and the Hereafter is superficial.
Besides, there are also those munafiqs who are foremost in joining the society of the believers by believing yet then lose faith and leave them. Those are the ones who turn away from Faith after accepting Islam. However, they commit a great sin as they break a promise given to Allah SWT and the believers that they would be persistent in their Faith and be loyal to them. This is why they are referred to in the Quran as Those who break Allah SWTs Covenant after it is ratified (Al-Baqara: 27)
In one of the Hadiths of Prophet Muhammad SAW, it is said that a hypocrite, when he speaks, tells lies, when he promises, breaks his promise. They abandon the believers in a slightest moment of difficulty and side with the adversaries of the believers. Their real character is revealed in times of distress.
As seen, the munafiq forgets about his previous promises at the moment of difficulty and displays a disloyal conduct. He is always prone to be capsized and lose his already tottering belief. This is because he does not believe in Allah SWT and the hereafter truly, although he says that he does. While the believers under the command of Prophet Muhammad SAW fought against the unbelievers, a group among them lost their faith against the enemy. They started to imagine various vain thoughts about Allah SWT and His prophet; and thus showed their real faces: In that situation were the Believers tried: they were shaken as by a tremendous shaking. And behold! The hypocrites and those in whose hearts is a disease (even) say: Allah SWT and His Messenger promised us nothing but delusion! (Al-Ahzab: 11-12).
On the other hand, the believers never showed weakness; and on the contrary, they were fortified in their faith. When the Believers saw the Confederate forces, they said: This is what Allah SWT and his Messenger had promised us, and Allah SWT and His Messenger told us what was true. And it only added to their faith and their zeal in obedience. (Al-Ahzab: 22).
After turning away from Allah SWTs religion, an eternal penalty starts for the munafiqs. This penalty starts in this world and continues till eternity. Verily Allah SWT will not deal unjustly with man in aught: It is man that wrongs his own soul. (Yunus: 44)
To the Hypocrites give the glad tidings that there is for them (but) a grievous penalty; (An-Nisaa: 138)
Already has He sent you Word in the Book, that when ye hear the signs of Allah SWT held in defiance and ridicule, ye are not to sit with them unless they turn to a different theme: if ye did, ye would be like them. For Allah SWT will collect the hypocrites and those who defy faith - all in Hell. (An-Nisaa: 140)
In this matter, the warning of Allah SWT is very clear and so explicit. Allah SWT has promised very painful punishments fore these munafiq people and they will be left in abject conditions. They will be thrown into the deepest hell i.e. Jahanam along with the kafirs.