The holy book of Quran and many other traditions have given their opinion regarding a person who doesn’t offer pray or who ignores it. We’ll mention just some of them.
“ O you who have believed, take not those who have taken your religion in ridicule and amusement among the ones who were given the Scripture before you nor the disbelievers as allies. And fear Allah, if you should [truly] be believers. (57) And when you call to prayer, they take it in ridicule and amusement. That is because they are a people who do not use reason. (58) Say, "O People of the Scripture, do you resent us except [for the fact] that we have believed in Allah and what was revealed to us and what was revealed before and because most of you are defiantly disobedient?" (59) Say, "Shall I inform you of [what is] worse than that as penalty from Allah? [It is that of] those whom Allah has cursed and with whom He became angry and made of them apes and pigs and slaves of Taught. Those are worse in position and further astray from the sound way."[1]
In the above verses people who don’t offer prayers, are cursed and disfavored from God, and they are promised to be punished on the Day of Judgment.
But there came after them successors who neglected prayer and pursued desires; so they are going to meet evil[2]
[Who will be] in gardens, questioning each other (40) About the criminals, (41) [And asking them], "What put you into Saqar?" (42) They will say, "We were not of those who prayed, (43) Nor did we used to feed the poor. (44) And we used to enter into vain discourse with those who engaged [in it], (45) And we used to deny the Day of Recompense.[3]
Hazrate Imam Sadiq (A.S) has quoted from the prophet (peace be upon him) that he stated: whoever ignore prayer, by oath of God he’ll not get access to meet me at Kousar Pool (Houdz Kousar).[4]
Imam Jafer Sadiq (A.S) has quoted again from the prophet (peace be upon him) that he stated: Devil (satan) is afraid and scream until the people offer their five times prayers on time, but when the people leave or ignore their prayer devil easily drive them crazy and take them to all evil acts.[5]
The prophet (peace be upon him) stated:
لاسهم في الاسلام لمن لا صلوة له. [6]
Whoever doesn’t offer his prayer, doesn’t have any share in Islam.
And he stated:
لكي شيء آفة و آفة الدين ترك الصلوة[7]
There is fall for everything which collapses it, and fall of religion is ignoring prayer.
The last will to his relatives:
Abu Basir says: After the martyrdom of Imam Sadiq (A.S) I went to his house to offer my condolences. When I entered into the house Ummeh Hameedeh saw me and started to cry, I also cried and then she said: if you would see Imam while he was leaving this world, you would get surprised, he in his last moments opened eyes and said call to all relatives, I did so, and then he stated: whoever ignore prayer will not get our intersession.[8]
[1] . يَا أَيُّهَا الَّذِينَ آمَنُوا لَا تَتَّخِذُوا الَّذِينَ اتَّخَذُوا دِينَكُمْ هُزُوًا وَلَعِبًا مِّنَ الَّذِينَ أُوتُوا الْكِتَابَ مِن قَبْلِكُمْ وَالْكُفَّارَ أَوْلِيَاءَ ۚوَاتَّقُوا اللَّـهَ إِن كُنتُم مُّؤْمِنِينَ ﴿٥٧﴾ وَإِذَا نَادَيْتُمْ إِلَى الصَّلَاةِ اتَّخَذُوهَا هُزُوًا وَلَعِبًا ۚ ذَٰلِكَ بِأَنَّهُمْ قَوْمٌ لَّا يَعْقِلُونَ ﴿٥٨﴾ قُلْ يَا أَهْلَ الْكِتَابِ هَلْ تَنقِمُونَ مِنَّا إِلَّا أَنْ آمَنَّا بِاللَّـهِ وَمَا أُنزِلَ إِلَيْنَا وَمَا أُنزِلَ مِن قَبْلُ وَأَنَّ أَكْثَرَكُمْ فَاسِقُونَ ﴿٥٩﴾ قُلْ هَلْ أُنَبِّئُكُم بِشَرٍّ مِّن ذَٰلِكَ مَثُوبَةً عِندَ اللَّـهِ ۚ مَن لَّعَنَهُ اللَّـهُ وَغَضِبَ عَلَيْهِ وَجَعَلَ مِنْهُمُ الْقِرَدَةَ وَالْخَنَازِيرَ وَعَبَدَ الطَّاغُوتَ ۚ أُولَـٰئِكَ شَرٌّ مَّكَانًا وَأَضَلُّ عَن سَوَاءِ السَّبِيلِ (Sura: Al-Ma'ida, verse: 57-60)
[2] . فَخَلَفَ مِن بَعْدِهِمْ خَلْفٌ أَضَاعُوا الصَّلَاةَ وَاتَّبَعُوا الشَّهَوَاتِ ۖ فَسَوْفَ يَلْقَوْنَ غَيًّا (Sura: Maryam, Verse: 59)
[3] . فِي جَنَّاتٍ يَتَسَاءَلُونَ ﴿٤٠﴾ عَنِ الْمُجْرِمِينَ ﴿٤١﴾ مَا سَلَكَكُمْ فِي سَقَرَ ﴿٤٢﴾ قَالُوا لَمْ نَكُ مِنَ الْمُصَلِّينَ ﴿٤٣﴾ وَلَمْ نَكُ نُطْعِمُ الْمِسْكِينَ ﴿٤٤﴾ وَكُنَّا نَخُوضُ مَعَ الْخَائِضِينَ ﴿٤٥﴾ وَكُنَّا نُكَذِّبُ بِيَوْمِ الدِّينِ (Sura: Al-Muddathir 74, verses: 40-46)
[4] . "قال رسول الله ليس مني من استخف بالصلاة لا يرد علي الحوض لا والله" Ellal Sharayeh: 2/365, Chapter: 70, tradtion No: 2; Bihar –al- Anwar: 80/9, chapter 6, tradition No: 4.
[5] . "عن الصادق عن آبائه (ع) قال: قال رسول الله (ص): لايزال الشيطان هائبا لابن آدم ذعرا منه ما صلي الصلوات الخمس لوقتهن فإذا ضيعهن اجترأ عليه فأدخله في العظائم" Al-Amaali, Shaikh Sadooq: 484, Majlis 73, Tradition No 9; Bihar Al-Anwar: 80/11, Chapter 6, Tradition No: 12.
[6] . Kanzil Al-Aamal: 7/327, tradition 19098; Al-Dur Al-Mansoor: 1/295
[7] . Israr Al-Salat: 27
[8] . "عن ابي بصير قال: دخلت علي أم حميدة أعزيها بأبي عبدالله الصادق (ع) فبكت و بكيت لبكائها ثم قالت يا أبا محمد لو رأيت أبا عبدالله (ع) عندالموت لرأيت عجبا فتح عينيه ثم قال: اجمعوا إلي كل من بيني و بينه قرابة قالت: فلم نترك أحدا إلاجمعناه قالت فنظر إليهم ثم قال: إن شفاعتنا لا تنال مستخفا باالصلاة" Al-Amaali, Shaikh Sadooq: 484, Majles 73, Tradition No:10; Bihar Al-Anwar: 80/19, chapter 6, Tradition No: 31.
source : GREATER SINS by Ayatullah-ul-Uzma Sayed Abdul Husain Dastghaib Shirazi (r.a.)