Answer
✅Answer: First, pay attention to the following hadith:
عَنْ أَبِي عَمْرٍو الزُّبَيْرِيِّ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ قُلْتُ لَهُ أَخْبِرْنِى عَنْ وُجُوهِ الْكُفْرِ فِى كِتَابِ اللَّهِ عَزَّوَجَلَّ قَالَ الْكُفْرُ فِى كِتَابِ اللَّهِ عَلَى خَمْسَةِ أَوْجُهٍ فَمِنْهَا كُفْرُ الْجُحُودُ وَ الْجُحُودُ عَلَى وَجْهَيْنِ وَ الْكُفْرُ بِتَرْكِ مَا أَمَرَ اللَّهُ وَ كُفْرُ الْبَرَاءَةِ وَ كُفْرُ النِّعَمِ..
📚 Al-Kafi, Vol. 2, p. 389
Translation: Abu 'Umar al-Zubayri says: I said to Imam Al-Sadiq (peace be upon him): 'Inform me of the number of ways 'kufr' (disbelief) is mentioned in the book of Allah, the Almighty and Glorious (the Qur'an)?' He said: 'Kufr in the book of Allah is of five types: the kufr of rejection, which is of two kinds; the kufr of abandoning what Allah has commanded; the kufr of disavowal; and the kufr of blessings...'
✅In the above hadith, which is recommended to be read in its entirety in the book 'Usul al-Kafi,' five types of disbelief are introduced, two of which are:
1- The kufr of rejection and denial of a truth that has become clear to the person.
2- The kufr due to abandoning divine commands (obligations).
✅People abandon prayer in two ways: some abandon prayer out of negligence, laziness, and disrespect, while others abandon the obligation of prayer out of denial.
✅According to the narrations, both groups of those who abandon prayer are disbelievers, and the difference between them is that the first group falls into the kufr of abandoning divine commands and obligations, while the second group falls into the second type of the kufr of rejection.
✅Several narrations regarding the one who abandons prayer and other obligations falling into disbelief by abandoning what Allah has commanded:
عَنْ زُرَارَةَ عَنْ أَبِی جَعْفَرٍ فِی حَدِیثِ عَدَدِ النَّوَافِلِ قَالَ إِنَّمَا هَذَا کُلُّهُ تَطَوُّعٌ وَ لَیْسَ بِمَفْرُوضٍ إِنَّ تَارِکَ الْفَرِیضَةِ کَافِرٌ وَ إِنَّ تَارِکَ هَذَا لَیْسَ بِکَافِرٍ
📚 Al-Tahdhib, Vol. 2, p. 8
Translation: Imam Al-Baqir (peace be upon him) said in a hadith about the number of supererogatory prayers: 'All of these supererogatory prayers are voluntary and recommended, not obligatory. Indeed, the one who abandons an obligation is a disbeliever, and indeed the one who abandons these supererogatory prayers is not a disbeliever.'
عن الصادق فی حدیث ٍ:کُلُّ مَنْ تَرَکَ الصَّلَاةَ قَاصِداً لِتَرْکِهَا فَلَیْسَ یَکُونُ قَصْدُهُ لِتَرْکِهَا اللَّذَّةَ فَإِذَا نُفِیَتِ اللَّذَّةُ وَقَعَ الِاسْتِخْفَافُ وَ إِذَا وَقَعَ الِاسْتِخْفَافُ وَقَعَ الْکُفْرُ
📚 Al-Kafi, Vol. 2, p. 386
Translation: Imam Al-Sadiq (peace be upon him) said in a hadith: 'Whoever abandons prayer intentionally, his intention in abandoning prayer is not for pleasure. So when pleasure is absent, contempt and disrespect occur, and when contempt and disrespect occur, disbelief occurs.'
عَنْ أَبِی عَبْدِ اللَّهِ فِی حَدِیثِ الْکَبَائِرِ قَالَ إِنَّ تَارِکَ الصَّلَاةِ کَافِرٌ یَعْنِی مِنْ غَیْرِ عِلَّةٍ
📚 Al-Kafi, Vol. 2, p. 279
Translation: Imam Al-Sadiq (peace be upon him) said in a hadith about major sins: 'The one who abandons prayer without a reason is a disbeliever.'
✅The Messenger of Allah (peace be upon him and his family) said: 'There is nothing between a Muslim and becoming a disbeliever except the intentional abandonment of an obligatory prayer or treating the prayer lightly and neglecting it and not praying it.'
📚 Al-Mahasin, Vol. 1, p. 80
✅As for the narrations of the one who denies prayer falling into the kufr of rejection:
قال الصادق فی حدیثٍ:إِنَّ اللَّهَ عَزَّ وَ جَلَّ فَرَضَ فَرَائِضَ مُوجَبَاتٍ عَلَی الْعِبَادِ فَمَنْ تَرَکَ فَرِیضَةً مِنَ الْمُوجَبَاتِ فَلَمْ یَعْمَلْ بِهَا وَ جَحَدَهَا کَانَ کَافِراً
📚 Al-Kafi, Vol. 2, p. 383
Translation: Imam Al-Sadiq (peace be upon him) said in a hadith: 'Indeed, Allah, the Almighty and Glorious, has made obligations compulsory for His servants, so whoever abandons an obligation from the mandatory duties and does not perform it and denies it, is a disbeliever.'
مُحَمَّدِ بْنِ مُسْلِمٍ قَالَ سَمِعْتُ أَبَا جَعْفَرٍ یَقُولُ کُلُّ شَیْ ءٍ یَجُرُّهُ الْإِقْرَارُ وَ التَّسْلِیمُ فَهُوَ الْإِیمَانُ وَ کُلُّ شَیْ ءٍ یَجُرُّهُ الْإِنْکَارُ وَ الْجُحُودُ فَهُوَ الْکُفْرُ
📚 Al-Kafi, Vol. 2, p. 387
Translation: Muhammad ibn Muslim says: 'I heard Imam Al-Baqir (peace be upon him) say: 'Everything that leads to confession and submission is faith, and everything that leads to denial and rejection is disbelief.''
✅It was said to Amir al-Mu'minin (peace be upon him): 'Is a person who says the two testimonies (shahadatayn) a believer?' He said: 'Then what about the divine obligations?... So for what reason does the one who denies the obligations become a disbeliever?'
(Meaning, a person who denies the divine obligations such as prayer, fasting, zakat, Hajj, and wilayah is a disbeliever).
✅There are numerous narrations for both types of disbelief that the one who abandons prayer falls into, although in the narrations, the disbelief of abandoning prayer accompanied by its denial and rejection is much more severe.