It is mentioned in Sahih Muslim Kitab al Iman that Jabir ra heard the Apostle (may peace and blessings be upon him) saying. Verily between man and between polytheism and unbelief is the negligence of prayer.
Imam an-Nawawi quoted the four school of thoughts under this hadith
Imam an-Nawawi said
وإن كان تركه تكاسلا مع اعتقاده وجوبها كما هو حال كثير من الناس فقد اختلف العلماء فيه ، فذهب مالك والشافعي رحمهما الله والجماهير من السلف والخلف إلى أنه لا يكفر بل يفسق ويستتاب فإن تاب وإلا قتلناه حدا كالزاني المحصن ، ولكنه يقتل بالسيف . وذهب جماعة من السلف إلى أنه يكفر وهو مروي عن علي بن أبي طالب كرم الله وجهه وهو إحدى الروايتين عن أحمد بن حنبل – رحمه الله – . وبه قال عبد الله بن المبارك وإسحاق بن راهويه . وهو وجه لبعض أصحاب الشافعي رضوان الله عليه . وذهب أبو حنيفة وجماعة من أهل الكوفة والمزني صاحب الشافعي رحمهما الله أنه لا يكفر ، ولا يقتل ، بل يعزر ويحبس حتى يصلي واحتج من قال بكفره بظاهر الحديث الثاني المذكور ، وبالقياس على كلمة التوحيد . واحتج من قال لا يقتل بحديث لا يحل دم امرئ مسلم إلا بإحدى ثلاث وليس فيه الصلاة . واحتج الجمهور على أنه لا يكفر بقوله تعالى : إن الله لا يغفر أن يشرك به ويغفر ما دون ذلك لمن يشاء وبقوله – صلى الله عليه وسلم – : من قال لا إله إلا الله دخل الجنة ومن مات وهو يعلم أن لا إله إلا الله دخل الجنة ولا يلقى الله تعالى عبد بهما غير شاك فيحجب عن الجنة . حرم الله على النار من قال لا إله إلا الله وغير ذلك .
If he does not pray because he is lazy, although he believes that it is obligatory – as is the case with many people – then the scholars differed concerning him. Maalik and ash-Shfa’i (may Allah have mercy on them) and the majority of the earlier and later scholars were of the view that he is not a disbeliever; rather he is a sinner who should be asked to repent. If he repents, all well and good; otherwise, he is to be executed as a hadd punishment, like the married adulterer, except that he should be killed by the sword. On the other hand, a number of the earlier generations were of the view that he is a disbeliever. This was narrated from ‘Ali ibn Abi Tatlib and is mentioned in one of the two reports from Ahmad ibn Hanbal (may Allah have mercy on him). It was also the view of Abdullah ibn alMubarak, Ishaq ihn Raahwayh and some of the followers of ashShafa’i.
Abu Haneefah and a number of the people of Kufah, as well as al-Muzani, the companion of ashShafa’i, were of the view that he is not a disbeliever and is not to be executed; rather he should he given a disciplinary punishment and imprisoned until he start to pray.
And the one who opted for his kufr he acted on apparent meaning of the second hadith mentioned (i.e. hadith of Jabir ra) and qiyas on Kalimah tul tawheed.
And those who say he will not be killed take evidence from the hadeeth which states it is not halal to kill Muslim apart from three things, and salah is not mentioned in that hadith.
The Majority of he scholars who say he has not done kufr take evidence from the verse “Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills.”
and from the hadith
“Messenger of Allah (peace be upon him) said. He who recites There is no god but Allah will enter Paradise, he who died knowing (fully well) that there is no god but Allah entered Paradise.”
and “without entertaining any doubt about these (two fundamentals),and will not be banished from entering Jannah.”
and “Allah prohibited the fire on him who recites There is no god but Allah” and other ahadith like these.
[Sharah Sahih Muslim Kitab al Eeman under the hadith of Jabir ra]
Ibn Kathir said
(And if two parties among the believers fall to fighting, then make peace between them both.) Therefore, Allah calls both opposing groups among Muslims, believers, although they are fighting each other. Al-Bukhari and other scholars relied on this Hadith as evidence that committing a sin does not nullify faith, NO MATTER HOW MAJOR THE SIN IS. This creed contradicts the creed of the Khawarij sect and those who accepted their idea, such as the Mu`tazilah sect. Al-Bukhari narrated that Al-Hasan said that Abu Bakrah said that the Messenger of Allah gave a speech on the Minbar while Al-Hasan bin `Ali was with him. He was repeatedly looking at Al-Hasan and then at the people; then said,
(Verily, this son of mine is a Sayyid (chief or master), and may Allah make peace between two great groups of Muslims through him.) What the Prophet said, occurred. Al-Hasan brought peace between the people of Ash-Sham and `Iraq, after they fought tremendous wars and frightening battles. [Tafsir Ibn Kathir under al Hujuraat verse 9]
Ibn Qudama al Hanbalee said
وَلِأَنَّ ذَلِكَ إجْمَاعُ الْمُسْلِمِينَ، فَإِنَّا لَا نَعْلَمُ فِي عَصْرٍ مِنْ الْأَعْصَارِ أَحَدًا مِنْ تَارِكِي الصَّلَاةِ تُرِكَ تَغْسِيلُهُ، وَالصَّلَاةُ عَلَيْهِ، وَدَفْنُهُ فِي مَقَابِر الْمُسْلِمِينَ، وَلَا مُنِعَ وَرَثَتُهُ مِيرَاثَهُ، وَلَا مُنِعَ هُوَ مِيرَاثَ مُوَرِّثِهِ، وَلَا فُرِّقَ بَيْنَ زَوْجَيْنِ لِتَرْكِ الصَّلَاةِ مِنْ أَحَدِهِمَا؛ مَعَ كَثْرَةِ تَارِكِي الصَّلَاةِ، وَلَوْ كَانَ كَافِرًا لَثَبَتَتْ هَذِهِ الْأَحْكَامُ كُلُّهَا، وَلَا نَعْلَمُ بَيْنَ الْمُسْلِمِينَ خِلَافًا فِي أَنَّ تَارِكَ الصَّلَاةِ يَجِبُ عَلَيْهِ قَضَاؤُهَا، وَلَوْ كَانَ مُرْتَدًّا لَمْ يَجِبُ عَلَيْهِ قَضَاءُ صَلَاةٍ وَلَا صِيَامٍ.
It is consensus of Muslims (that the Janazah of taruk as-salah will be prayed), and I don’t know any era where ghusl of the deceased was abandoned, or his Slat al Janaza was not prayed or he was not buried in the Muslim`s graveyard, or his household were stopped to take from the inheritance or Taruk as-salah was stopped to take inheritance or neither the nikah is affected if anyone among the husband and wife are taruk as-salah, If this type of person is Kafir then these rulings would apply on him, and I don’t know any difference of opinion among the Muslims that it is Wajib on Taruk as-salah to do qadha, if taruk as-salah was a kafir then qadha of salah and siyaam wouldn’t be wajib on him. [al Mughni 2/33]
Shaykh Ibn Taymiyah said
ولهذا لم يعلم انم أحدا من تاركي الصلاة ترك غسله والصلاة عليه ودفنه مع المسلمين ولا منع ورثته ميراثه ولا إهدار دمه بسبب ذلك مع كثرة تاركي الصلاة في كل عصر والأمة لا تجتمع على ضلالة
It is not known that the ghusl of Taruk as-salah was abandon up till today or his salat al janazah was abandoned, or he was not buried in Muslim`s graveyard or his relatives were not given his inheritance.. When there are many taruk as-salah in every era, the Ummah can not unite on misguidance. [Shrah Umda tul fiqh p 91]
Ibn Abdul Bar
He said while explaining the Word “Kufr” as appears to be in the Hadith of Abandoning Salah :
أن تارك الصلاة إذا كان مقرا غير جاحد ولا مستكبر ، فاسق مرتكب لكبيرة موبقة من الكبائر الموبقات ، وهو مع ذلك في مشيئة الله – عز وجل – إن شاء غفر له ، وإن شاء عذبه ، فإنه لا يغفر أن يشرك به ، ويغفر ما دون ذلك لمن يشاء ، وقد يكون الكفر يطلق على من لم يخرج من الإسلام ،
If the one who Abandons Prayer if he affirms in it doesn’t deny it and doesn’t not arrogantly (rejects it), is a Faasiq (transgressor) committer of the Major Graveious Sin amongst the Major Graveious Sin and along with this he is under the Will of Allah swt if he wants he could punish him or he could forgive him, and He doesn’t forgive who associates partners with him except that he forgets to whom he wants.
And The Kufr Sometimes Applied on the things from which a person doesn’t get out the fold of Islam. (end quote)
Then he said:
فيحتمل – والله أعلم – إطلاق الكفر على تارك الصلاة أن يكون معناه أن تركه الصلاة غطى إيمانه وغيبه حتى صار غالبا عليه ، وهو مع ذلك مومن باعتقاده
And its likely to be possible – And Allah Knows Best – that the Kufr applied on the abandoning Salah has the meaning that the one who abandons salah his Emaan is covered and unseen until this becomes very often on him, and along with this he is a Momin with his Belief. [at-Tamheed li Ibn Abdul barr]
Hafidh Ibn Hajr al asqalani
He said under the words of Prophet peace be upon him ” I have been given the right of intercession” [Sahih al-Bukhari 335]
He commented
فالظاهر أن المراد بالشفاعة المختصة في هذا الحديث إخراج من ليس له عمل صالح إلا التوحيد
Apparently the meaning of intercession specified in this hadith (is) bringing out who doesn’t have any good deed except Tawheed.
(Fath Ul Bari 13/503)