The Reckoning is one of the most terrifying of all stages/stages of the hereafter, so much so that the hereafter is often referred to, as a whole, as "the Day of Reckoning". Numerous verses in the Holy Qur'an refer to it, emphasizing its significance and urging the faithful to prepare themselves for it with good deeds and acts of adoration, the latter cannot be accepted if the former are not. Some of the verses which refer to reckoning and to the fact that people take it lightly are these:

 بسم الله الرحمن الرحيم. اقْتَرَبَ لِلنَّاسِ حِسَابُهُمْ وَهُمْ فِي غَفْلَةٍ مُّعْرِضُونَ، مَا يَأْتِيهِم مِّن ذِكْرٍ مَّن رَّبِّهِم مُّحْدَثٍ إِلاَّ اسْتَمَعُوهُ وَهُمْ يَلْعَبُونَ، لاهِيَةً قُلُوبُهُمْ وَأَسَرُّواْ النَّجْوَى الَّذِينَ ظَلَمُواْ: هَلْ هَذَا إِلاَّ بَشَرٌ مِّثْلُكُمْ؟ أَفَتَأْتُونَ السِّحْرَ وَأَنتُمْ تُبْصِرُونَ؟ قَالَ رَبِّي يَعْلَمُ الْقَوْلَ فِي السَّمَاء وَالأَرْضِ وَهُوَ السَّمِيعُ الْعَلِيمُ، بَلْ قَالُواْ أَضْغَاثُ أَحْلامٍ، بَلِ افْتَرَاهُ، بَلْ هُوَ شَاعِرٌ، فَلْيَأْتِنَا بِآيَةٍ كَمَا أُرْسِلَ الأَوَّلُونَ: مَا آمَنَتْ قَبْلَهُم مِّن قَرْيَةٍ أَهْلَكْنَاهَا، أَفَهُمْ يُؤْمِنُونَ؟

"In the name of Allah‎, the Most Gracious, the Most Merciful. Mankind's reckoning comes closer and closer: Yet they do not heed, and they turn away. (Nothing) ever comes to them of a renewed message from their Lord except that they listen to it as in jest, their hearts toying with trifles. The wrongdoers conceal their private counsels (saying), 'Is this more than a man like your own selves? Will you yield to witchcraft with your eyes open?' Say: 'My Lord knows (every) word (spoken) in the heavens and the earth: He is the One Who hears and knows (all things).' 'No,' they say, '(these are) medleys of dreams! No, he forged it! No, he is (but) a poet! Then let him bring us a Sign like the ones that were sent to (Prophets) of old!' (As for those) before them, not one of the populations which We destroyed believed: Will these believe?" (Qur'an, 21:1-6). Another reference is this:

وَكَأَيِّن مِّن قَرْيَةٍ عَتَتْ عَنْ أَمْرِ رَبِّهَا وَرُسُلِهِ فَحَاسَبْنَاهَا حِسَابًا شَدِيدًا وَعَذَّبْنَاهَا عَذَابًا نُّكْرًا، فَذَاقَتْ وَبَالَ أَمْرِهَا وَكَانَ عَاقِبَةُ أَمْرِهَا خُسْرًا: أَعَدَّ اللَّهُ لَهُمْ عَذَابًا شَدِيدًا فَاتَّقُوا اللَّهَ يَا أُولِي الأَلْبَابِ الَّذِينَ آمَنُوا قَدْ أَنزَلَ اللَّهُ إِلَيْكُمْ ذِكْرًا: رَّسُولا يَتْلُو عَلَيْكُمْ آيَاتِ اللَّهِ مُبَيِّنَاتٍ لِّيُخْرِجَ الَّذِينَ آمَنُوا وَعَمِلُوا الصَّالِحَاتِ مِنَ الظُّلُمَاتِ إِلَى النُّور،ِ وَمَن يُؤْمِن بِاللَّهِ وَيَعْمَلْ صَالِحًا يُدْخِلْهُ جَنَّاتٍ تَجْرِي مِن تَحْتِهَا الأَنْهَارُ خَالِدِينَ فِيهَا أَبَدًا، قَدْ أَحْسَنَ اللَّهُ لَهُ رِزْقًا

How many generations that insolently opposed their Lord's command and (that) of His Prophets did We call to account, to a severe account? And We imposed on them an exemplary punishment. Then they tasted the evil result of their conduct, and the end of their conduct was perdition. Allah‎ has prepared a severe punishment for them (in the hereafter). So fear Allah‎, O you men of understanding who have believed, for Allah‎ has indeed sent down a message for you, a Prophet who rehearses God's Signs to you, containing clear explanations, so that he may lead forth those who believe and do righteous deeds from the depths of darkness into the light. And those who believe in Allah‎ and do righteous deeds He will admit into gardens beneath which rivers flow to dwell therein forever: Allah‎ has indeed granted a most excellent provision for them" (Qur'an, 65:8-11). Just as there are numerous references to reckoning in the Holy Qur'an, there are also numerous references to it in the Sunnah of the Prophet (P): Many traditions warn the believers about its woes and perils. On p. 258, Vol. 7 of Bihar al-Anwar, we read the following:

روى الشيخ الصدوق (رحمة الله عليه) عن طريق أهل البيت (عليهم السلام) أنه قال رسول الله (صلى الله عليه و آله و سلم): لا تتحرك قدما عبد من عباد الله، إلا و أن يسأل عن أربعه: عن عمره فيم أفناه، و عن شبابه فيم قضاه، و عن ماله من أين وجده، و فيم صرفه، و عن محبتنا نحن أهل البيت

Sheikh as-Saduq (may Allah‎ have mercy on him) has narrated through the path of Ahl al-Bayt (peace with them) saying that the Messenger of Allah‎ (peace and salutation of Allah‎ be with him and his progeny) said: "The feet of a servant of Allah‎ do not move before he is asked about four things: his lifespan and how he spent it, his youth and what he did during it, his wealth and where he found it and how he spent it and about love for us, we Ahl al-Bayt (as)." On p. 267 of the same reference, we read the following:

روى الشيخ الطوسي (رحمة الله عليه) عن الامام الباقر (عليه السلام) أنه قال: أول ما يحاسب عنه العبد الصلاة، إن قبلت قبل ما سواها

Sheikh at-Tusi (may Allah‎ have mercy on him) has narrated from Imam‎ al-Baqir (peace with him) saying: "The first thing about which a servant of Allah‎ is questioned is prayer. If it is accepted, everything else is accepted." On p. 274 of the same reference, we read the following:

روى الشيخ الصدوق أن الدائن يأتي يوم القيامة و يشتكي، فاذا كان للمدين حسنات، تؤخذ منه للدائن، و ان لم تكن له حسنات، فتؤخذ من معاصي الدائن و تضاف الى معاصي المدين.

"Sheikh as-Saduq‎ has narrated saying that the creditor comes on the Judgment Day and complains. If the borrower has good deeds, they (some of them if not all) will be taken away and given to the creditor. But if he has no good deeds, some of the sins of the creditor will be taken and added to those of the borrower." On p. 82 of Manazil al-Akhira, we read the following:

إعلم أن بعض المحققين قد قال: لا ينجو من مخاطر الحساب و دقائق الميزان إلا من حاسب نفسه في الدنيا و آختبر شخصه بميزان الشرع الاسلامي و كذلك أعماله و أقواله و أفعاله و سيئاته و لحظاته و حركاته و سكناته، فقد قالوا: حاسبوا أنفسكم قبل أن تحاسبوا

"Be informed that some critics have said: Nobody is spared the perils of reckoning and the precisions of the scales except one who holds himself to account in the short life and tests his person according to the scales of the Islamic Shari`a, applying the same to his actions, statements, deeds, sins, looks, motion and stillness, for they have said: Hold yourselves to account before you yourselves are held to account."