Imam Ali (peace be upon him) said, in reply to a heretic who claimed there were contradictions in the Quran: "As for the words of Allah the Exalted: یَوْمَ یَقُومُ الرُّوحُ وَ الْمَلائِکَةُ صَفًّا لا یَتَکَلَّمُونَ إِلَّا مَنْ أَذِنَ لَهُ الرَّحْمنُ وَ قالَ صَواباً [The day when the Spirit and the angels stand in a row, none shall speak except one whom the Most Merciful permits, and he says what is right] (al-Naba' 78:38), and the words of Allah the Mighty and Majestic: وَ اللَّهِ رَبِّنا ما کُنَّا مُشْرِکِینَ [By Allah, our Lord, we were not polytheists] (al-An'am 6:23), and the words of Allah the Mighty and Majestic: 'Then on the Day of Resurrection you will renounce each other and curse each other' (al-'Ankabut 29:25) — each of these belongs to one of the stations of that Day whose length is fifty thousand years. What is meant is that the people of sins reject and curse one another. Then they gather in another station and weep bitterly there. Then they gather in another station and are made to speak (istintaq), and they say: وَ اللَّهِ رَبِّنا ما کُنَّا مُشْرِکِینَ [By Allah, our Lord, we were not polytheists] (al-An'am 6:23). These are specifically those who in the abode of this world confessed the oneness of Allah, but their faith in Allah the Exalted does not benefit them, because they opposed His messengers and doubted what they brought from their Lord, and broke their covenants concerning their successors. Then Allah seals their mouths into silence and makes their hands, feet and skins speak, and these bear witness to every sin they committed. Then the seal is lifted from their tongues and they say to their skins: 'Why did you bear witness against us?' They answer: 'The same Allah who made every being speak has made us speak' (Fussilat 41:21). Then they gather in another station and, out of dread at the severity of the affair and the greatness of the trial they see, they flee from one another. Then they gather in another station and there the friends of Allah and His chosen ones are made to speak. None speaks except one whom the Most Merciful permits, and [when they speak] they say what is right (al-Naba' 78:38). At that time the messengers are made to stand and are asked about the delivery of the messages they carried to their peoples, and they report that they delivered the messages to their peoples. Then the peoples are questioned and they deny, as Allah the Exalted said: فَلَنَسْئَلَنَّ الَّذِینَ أُرْسِلَ إِلَیْهِمْ وَ لَنَسْئَلَنَّ الْمُرْسَلِینَ [Most certainly then We will question those to whom (the messengers) were sent, and most certainly We will question the messengers]. They say: ما جاءَنا مِنْ بَشِیرٍ وَ لا نَذِیرٍ [No bearer of glad tidings and no warner came to us]. Then the messengers call the Messenger of Allah (peace be upon him and his family) to witness, and he testifies to the truthfulness of the messengers and the falsehood of the peoples who deny, and he says to each of those peoples: بَلَی قَدْ جاءَکُمْ بَشِیرٌ وَ نَذِیرٌ وَ اللهُ عَلی کُلِّ شَیْءٍ قَدِیرٌ [Yes, a bearer of glad tidings and a warner did come to you, and Allah is Powerful over all things] (al-Ma'idah 5:19) — that is, He is able to have your own limbs bear witness against you that the messengers delivered their messages to you."