Imam Ali (peace be upon him): In a lengthy narration it is mentioned that a man from among the disbelievers came to Imam Ali (peace be upon him) and asked him about verses of the Quran that were difficult for him, thinking that these verses contradicted one another. Amir al-Mu'minin (peace be upon him) answered him, and in the end he became a Muslim. Among the things he said... As for the word of Allah the Exalted: يَوْمَ يَقُومُ الرُّوحُ وَ الْمَلائِكَةُ صَفًّا لا يَتَكَلَّمُونَ إِلَّا مَنْ أَذِنَ لَهُ الرَّحْمنُ وَ قالَ صَواباً [The day when the Spirit and the angels stand in a row, none shall speak except him to whom the Most Merciful gives permission, and he says what is right] (Naba/38), and they say: وَ اللهِ رَبِّنا ما كُنَّا مُشْرِكِينَ [By Allah, our Lord, we were not polytheists] (An'am/23), and: on the Day of Resurrection you will deny one another and curse one another (Ankabut/25), and: this quarrel of the people of Hell with one another is something that will truly occur (Sad/64), and: do not dispute in My presence, for I had already warned you of the punishment beforehand (Qaf/28), and: today We shall set a seal upon their mouths, and their hands will speak to Us and their feet will bear witness to what they used to do (Ya-Sin/65). Each of these belongs to one of the stations of that Day whose length is fifty thousand years... Then they gather in other stations, and there the friends of Allah and His chosen ones are made to speak, and none speaks except him to whom the Most Merciful gives permission, and he says what is good. At that time the messengers are made to stand, and they are asked about delivering the messages they carried to their nations, and they report that they have delivered the messages to their nations. Then the nations are asked, and they deny it, just as Allah the Exalted said: فَلَنَسْئَلَنَّ الَّذِينَ أُرْسِلَ إِلَيْهِمْ وَ لَنَسْئَلَنَّ الْمُرْسَلِينَ [Indeed, We shall question those to whom the messengers were sent, and We shall also question the messengers] (A'raf/6). They say: no bearer of glad tidings and no warner came to us. Then the messengers take the Messenger of Allah (peace be upon him and his family) as their witness, and he bears witness to the truthfulness of the messengers and to the lying of the denying nations, and says to each of those nations: 'Yes, indeed a bearer of glad tidings and a warner came to you, and Allah has power over all things.' That is, He is able to make your own limbs bear witness against you that the messengers delivered their messages to you; this is why Allah the Exalted said to His Prophet (peace be upon him and his family): فَكَيْفَ إِذا جِئْنا مِنْ كُلِّ أُمَّةٍ بِشَهِيدٍ وَ جِئْنا بِكَ عَلى هؤُلاءِ شَهِيداً [How then will it be when We bring from every nation a witness, and We bring you as a witness against these people?] (Nisa/41). At that point they will no longer be able to reject his testimony, because they fear that Allah will set a seal upon their mouths and that their limbs will bear witness against them concerning what they used to do.