The Signs of which Allah, the Most Holy, the Most High, has spoken in the Holy Quran are The Imams 
3 Aḥadīth
Al-Husayn ibn Muhammad has narrated from MuAlia ibn Muhammad from Ahmad ibn Muhammad ibn ’Abdallah from Ahmad ibn Hilal from ’Umayyah ibn Ali from Dawud al-Riqqi who has said that he asked Imam abu ‘Abdallah about the meaning of the words of Allah in the following verse. “The signs and warnings are of no avail to the disbelieving people.” (0:0) The Imams said, “Signs are the Imams and warnings are the prophets (s.a.).”
الْحُسَيْنُ بْنُ مُحَمَّدٍ عَنْ مُعَلَّى بْنِ مُحَمَّدٍ عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ عَبْدِ الله عَنْ أَحْمَدَ بْنِ هِلالٍ عَنْ أُمَيَّةَ بْنِ عَلِيٍّ عَنْ دَاوُدَ الرَّقِّيِّ قَالَ سَأَلْتُ أَبَا عَبْدِ الله عَنْ قَوْلِ الله تَبَارَكَ وَتَعَالَى وَما تُغْنِي الاياتُ وَالنُّذُرُ عَنْ قَوْمٍ لا يُؤْمِنُونَ قَالَ الايَاتُ هُمُ الائِمَّةُ وَالنُّذُرُ هُمُ الانْبِيَاءُ (عَلَيْهم السَّلام )
Ahmad ibn Mahran has narrated from ’Abd al-’Azim ibn ’Abdallah al-Hasani from Musa ibn Muhammad al-‘Ijli from Yunus ibn Ya‘qub (in a marfu‘ manner) that abu Ja’far has said about the words of Allah, the Most Holy, the Most High, “. . but they rejected all Our signs. .” (54:42) ‘The signs are all the successors (of the prophets (s.a.)
أَحْمَدُ بْنُ مِهْرَانَ عَنْ عَبْدِ الْعَظِيمِ بْنِ عَبْدِ الله الْحَسَنِيِّ عَنْ مُوسَى بْنِ مُحَمَّدٍ الْعِجْلِيِّ عَنْ يُونُسَ بْنِ يَعْقُوبَ رَفَعَهُ عَنْ ابي جعفر فِي قَوْلِ الله عَزَّ وَجَلَّ كَذَّبُوا بِآياتِنا كُلِّها يَعْنِي الاوْصِيَاءَ كُلَّهُمْ.
Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Muhammad Ibn Abi ‘Umayr or someone other than him from Muhammad ibn al-Fudayl from abu Hamzah who has that he said to abu Ja’far , “May Allah take my soul in service for your cause, the Shi‘a (your followers) ask about the meaning of the words of Allah, “Of what do they ask one another? (78:). Do they ask about the great news?”The Imams said, “It depends up on my decision. I may tell them or may not tell them. Then he said: “I like, however, to tell you the meaning thereof.” I then asked what is the meaning of, “Of what do they ask one another?” The Imams said, “It means Amir al-Mu’minin . Amir al-Mu’minin used to say, “None of the signs of Allah, the Most Holy, the Most High, is bigger than I and none of the news of Allah is greater than I.”
مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ مُحَمَّدِ بْنِ أَبِي عُمَيْرٍ أَوْ غَيْرِهِ عَنْ مُحَمَّدِ بْنِ الْفُضَيْلِ عَنْ أَبِي حَمْزَةَ عَنْ ابي جعفر قَالَ قُلْتُ لَهُ جُعِلْتُ فِدَاكَ إِنَّ الشِّيعَةَ يَسْأَلُونَكَ عَنْ تَفْسِيرِ هَذِهِ الايَةِ عَمَّ يَتَساءَلُونَ عَنِ النَّبَإِ الْعَظِيمِ قَالَ ذَلِكَ إِلَيَّ إِنْ شِئْتُ أَخْبَرْتُهُمْ وَإِنْ شِئْتُ لَمْ أُخْبِرْهُمْ ثُمَّ قَالَ لَكِنِّي أُخْبِرُكَ بِتَفْسِيرِهَا قُلْتُ عَمَّ يَتَساءَلُونَ قَالَ فَقَالَ هِيَ فِي أَمِيرِ الْمُؤْمِنِينَ صَلَوَاتُ الله عَلَيْهِ كَانَ أَمِيرُ الْمُؤْمِنِينَ صَلَوَاتُ الله عَلَيْهِ يَقُولُ مَا لله عَزَّ وَجَلَّ آيَةٌ هِيَ أَكْبَرُ مِنِّي وَلا لله مِنْ نَبَإٍ أَعْظَمُ مِنِّي.