Praise be to Allah.
The Muslim should not incline more towards one scholarly opinion rather than another just because it is in accordance with his whims and desires or his reasoning. Rather he has to accept the ruling based on evidence from the Qur’aan and Sunnah. It is essential to put the texts and rulings of sharee’ah before all else.
Apostasy (riddah) and going out of Islam are things that may be done in the heart, on the tongue or in one's actions.
Apostasy may take place in the heart, such as disbelieving in Allaah, or believing that there is another creator alongside Allaah, or hating Allaah or His Messenger (peace and blessings of Allaah be upon him).
Apostasy may take the form of words spoken on the tongue, such as defaming Allaah or the Messenger of Allaah (peace and blessings of Allaah be upon him).
Or apostasy may take the form of outward physical actions, such as prostrating to an idol, mistreating the Mus-haf, or not praying.
The apostate (murtadd) is worse than one who is a kaafir in the first place.
Shaykh al-Islam Ibn Taymiyah said, refuting the pantheistic belief of the Baatinis:
It is well known that the kaafir Tatars are better than these (Baatinis), because the latter are apostates from Islam, of the worst type of apostates. The apostate is worse than one who is a kaafir in the first place in many aspects.
Majmoo’ al-Fataawa, 1/193
Not every Muslim who falls into kufr is a kaafir and apostate. There are reasons why a Muslim may be excused and not judged to be a kaafir, for example: ignorance, misunderstanding, being forced, and making mistakes.
With regard to the first, a man may be ignorant of the ruling of Allaah, because he lives far from the Muslim lands, such as one who grows up in the desert or in a kaafir land, or has only recently come to Islam. This may include many of those Muslims who live in societies where ignorance prevails and knowledge is scarce. These are the ones concerning whom the questioner is confused as to whether they are to be judged as kaafirs and executed.
The second reason is if a person interprets the ruling of Allaah in a manner not intended by the Lawgiver, such as those who blindly follow the people of bid’ah (innovation) in their misinterpretations, such as the Murji’ah, Mu’tazilah, Khawaarij and the like.
The third reason is if an oppressor overwhelms a Muslim and will not let him go until he makes a blatant statement of kufr out loud in order to ward off the torture, when his heart is at ease with faith.
The fourth is when words of kufr come to one's lips without meaning it.
Not everyone who is ignorant about wudoo’ and prayer can be excused, when he sees the Muslims establishing prayer and praying regularly, and he can read and hear the verses on prayer. What is preventing him from praying or from asking about how it is done and what its essential conditions are?
The apostate is not to be put to death immediately after he falls into apostasy, especially if his apostasy happens because of some doubt that arose. Rather he should be asked to repent and he should be offered the opportunity to return to Islam and resolve his doubts, if he has any doubts. Then if he persists in his apostasy after that, he is to be put to death.
Ibn Qudaamah said in al-Mughni, 9/18:
The apostate should not be put to death until he has been asked to repent three times. This is the view of the majority of scholars, including ‘Umar, ‘Ali, ‘Ata’, al-Nakhaii, Maalik, al-Thawri, al-Awzaa’i, Ishaaq and others. Because apostasy comes about because of doubt, and cannot be dispelled in an instant. Time should be allowed for the person to rethink the matter, and the best length of time is three days.
The saheeh Sunnah indicates that it is essential to put the apostate to death.
Al-Bukhaari (6922) narrated that Ibn ‘Abbaas said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever changes his religion, put him to death.”
Al-Bukhaari (6484) and Muslim (1676) narrated that ‘Abd-Allaah ibn Mas’ood said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “It is not permissible to shed the blood of a Muslim who bears witness that there is no god except Allaah and that I am the Messenger of Allaah, except in one of three cases: a soul for a soul (i.e., in the case of murder); a previously-married person who commits zina; and one who leaves his religion and separates from the main body of the Muslims.”
The general meaning of these ahaadeeth indicates that it is essential to put the apostate to death whether he is waging war on Islam (muhaarib) or not.
The view that the apostate who is to be put to death is the one who is waging war on Islam (muhaarib) only is contrary to these ahaadeeth. The Prophet (peace and blessings of Allaah be upon him) said that the reason why he should be put to death is his apostasy, not his waging war against Islam.
Undoubtedly some kinds of apostasy are more abhorrent than others, and the apostasy of one who wages war against Islam is more abhorrent than that of anyone else. Hence some of the scholars differentiated between them, and said that it is not essential to ask the muhaarib to repent or to accept his repentance; rather he should be put to death even if he repents, whereas the repentance of one who is not a muhaarib should be accepted and he should not be put to death. This is the view favoured by Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him).
Apostasy is of two types: ordinary apostasy and extreme apostasy, for which execution is prescribed. In both cases there is evidence that it is essential to execute the apostate, but the evidence indicating that the sentence of death may be waived if the person repents does not apply to both types of apostasy. Rather the evidence indicates that that is allowed only in the first case – i.e., ordinary apostasy – as will be clear to anyone who studies the evidence that speaks about accepting the repentance of the apostate. In the second type – i.e., extreme apostasy – the obligation to put the apostate to death still stands, and there is no text or scholarly consensus to indicate that the death sentence may be waived. The two cases are quite different and there is no comparison between them. It does not say in the Qur’aan or Sunnah, or according to scholarly consensus, that everyone who apostatizes in word or deed may be spared the death sentence if he repents after he is a captured and tried. Rather the Qur’aan and Sunnah, and scholarly consensus, differentiate between the different kinds of apostates.
Al-Saarim al-Maslool, 3/696
Al-Hallaaj was one of the most well known heretics who were put to death without being asked to repent. Al-Qaadi ‘Iyaad said:
The Maaliki fuqaha’ of Baghdad at the time of al-Muqtadir were unanimously agreed that al-Hallaaj should be killed and crucified because of his claim to divinity and his belief in incarnation, and his saying “I am al-Haqq [God],” even though he outwardly appeared to adhere to sharee’ah, and they did not accept his repentance.
Al-Shifa bi Ta’reef Huqooq al-Mustafa, 2/1091.
Based on this, it is clear that what the questioner says about the apostate not being killed unless he is waging war on Islam is mistaken, and the differentiation that we have quoted from Shaykh al-Islam Ibn Taymiyah may dispel any confusion and make the matter clearer.
Waging war against Islam is not limited only to fighting with weapons, rather it may be done verbally such as defaming Islam or the Prophet (peace and blessings of Allaah be upon him), or attacking the Qur’aan, and so on. Waging verbal war against Islam may be worse than waging war against it with weapons in some cases.
Shaykh al-Islam Ibn Taymiyah said:
Muhaarabah (waging war against Islam) is of two types: physical and verbal. Waging war verbally against Islam may be worse than waging war physically – as stated above – hence the Prophet (peace and blessings of Allaah be upon him) used to kill those who waged war against Islam verbally, whilst letting off some of those who waged war against Islam physically. This ruling is to be applied more strictly after the death of the Prophet (peace and blessings of Allaah be upon him). Mischief may be caused by physical action or by words, but the damage caused by words is many times greater than that caused by physical action; and the goodness achieved by words in reforming may be many times greater than that achieved by physical action. It is proven that waging war against Allaah and His Messenger (peace and blessings of Allaah be upon him) verbally is worse and the efforts on earth to undermine religion by verbal means is more effective.
Al-Saarim al-Maslool, 3/735
With regard to not praying, the correct view is that the one who does not pray is a kaafir and an apostate. See question no. 5208.
And Allaah knows best.