✅Answer: Please pay attention to the following narrations:

1 عَنْ مُحَمَّدِ بْنِ الْفُضَيْلِ عَنِ الرِّضَا عَنْ آبَائِهِ قَالَ قَالَ رَسُولُ اللَّهِ يَا عَلِيُ‏ أَنْتَ‏ وَ الْأَئِمَّةُ مِنْ وُلْدِكَ بَعْدِي حُجَجُ اللَّهِ عَلَى خَلْقِهِ وَ أَعْلَامُهُ فِي بَرِيَّتِهِ فَمَنْ أَنْكَرَ وَاحِداً مِنْهُمْ فَقَدْ أَنْكَرَنِي وَ مَنْ عَصَا وَاحِداً مِنْهُمْ فَقَدْ عَصَانِي وَ مَنْ جَفَا وَاحِداً مِنْهُمْ فَقَدْ جَفَانِي وَ مَنْ وَصَلَكُمْ فَقَدْ وَصَلَنِي وَ مَنْ أَطَاعَكُمْ فَقَدْ أَطَاعَنِي وَ مَنْ وَالاكُمْ فَقَدْ وَالانِي وَ مَنْ عَادَاكُمْ فَقَدْ عَادَانِي لِأَنَّكُمْ مِنِّي خُلِقْتُمْ مِنْ طِينَتِي وَ أَنَا مِنْكُمْ.

📚 Kamal al-Din, Vol. 2, p. 413

The Messenger of Allah (peace be upon him and his family) said: 'O Ali, you and the leaders from your children after me are the proofs of Allah upon His creation and His signs among His creation, so whoever denies one of them has indeed denied me, and whoever disobeys one of them has indeed disobeyed me, and whoever is unjust to one of them has been unjust to me, and whoever connects with them has connected with me, and whoever obeys them has obeyed me, and whoever befriends them has befriended me, and whoever shows enmity to them has shown enmity to me, because indeed they (i.e., the 12 Imams) are from me and were created from my essence, and I am from them!'

2 عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ قَالَ: قُلْتُ لِأَبِي عَبْداللَّهِ رَجُلٌ قَالَ لِي اعْرِفِ‏ الْأَخِيرَ مِنَ‏ الْأَئِمَّةِ وَ لَا يَضُرُّكَ أَنْ لَا تَعْرِفَ الْأَوَّلَ قَالَ فَقَالَ لَعَنَ اللَّهُ هَذَا فَإِنِّي أُبْغِضُهُ وَ لَا أَعْرِفُهُ وَ هَلْ يُعْرَفُ الْأَخِيرُ إِلَّا بِالْأَوَّلِ.

📚 Ghaybah of Nu'mani, p. 64

Muhammad ibn Muslim said: I said to Imam Sadiq (peace be upon him) a man told me: 'Know the last Imam from the Imams, and not knowing the first Imam will not harm you!'

The Imam said: 'May Allah curse this person! Indeed, I dislike him while I do not know him, and is the last Imam known except through the first Imam?!'

3 عَنْ مُحَمَّدِ بْنِ تَمَّامٍ قَالَ: قُلْتُ لِأَبِي عَبْدِ اللَّهِ إِنَّ فُلَاناً مَوْلَاكَ يُقْرِئُكَ السَّلَامَ وَ يَقُولُ لَكَ اضْمَنْ لِيَ الشَّفَاعَةَ فَقَالَ أَ مِنْ مَوَالِينَا قُلْتُ نَعَمْ قَالَ أَمْرُهُ أَرْفَعُ مِنْ ذَلِكَ قَالَ قُلْتُ إِنَّهُ رَجُلٌ يُوَالِي عَلِيّاً وَ لَمْ يَعْرِفْ مِنْ بَعْدِهِ مِنَ الْأَوْصِيَاءِ قَالَ ضَالٌّ قُلْتُ فَأَقَرَّ بِالْأَئِمَّةِ جَمِيعاً وَ جَحَدَ الْآخِرَ قَالَ هُوَ كَمَنْ أَقَرَّ بِعِيسَى وَ جَحَدَ بِمُحَمَّدٍ أَوْ أَقَرَّ بِمُحَمَّدٍ وَ جَحَدَ بِعِيسَى نَعُوذُ بِاللَّهِ مِنْ جَحْدِ حُجَّةٍ مِنْ حُجَجِهِ.

📚 Ghaybah of Nu'mani, p. 55

Muhammad ibn Tamam said: I said to Imam Sadiq (peace be upon him), 'So-and-so, who is one of your friends, sends you greetings and asks you to guarantee intercession for him!' The Imam said: 'Is he from our followers?' I said: 'Yes!' He said: 'His matter (his status and position) is higher than this!'

I said: 'Indeed, he has the 'wilayah' and love of Imam Ali (peace be upon him) but he does not know the successors after him!'

The Imam said: 'He is misguided,' I said: 'If he acknowledges and accepts all the Imams but denies the last Imam (what is his state)?' He said: 'He is like one who acknowledges Jesus (peace be upon him and our Prophet and his family) but denies Muhammad (peace be upon him and his family) or acknowledges Muhammad (peace be upon him and his family) and denies Jesus (peace be upon him)! We seek refuge in Allah from denying a proof from His proofs!'

4 عَنِ ابْنِ مُسْکَانَ عَنْ أَبِی عَبْداللَّهِ علیه السلام قَالَ: مَنْ أَنْکَرَ وَاحِداً مِنَ الْأَحْیَاءِ فَقَدْ أَنْکَرَ الْأَمْوَاتَ

📚 Ikmal al-Din, p. 228

Imam Sadiq (peace be upon him) said: 'Whoever denies one of the living (Imams) has certainly denied the ones who have passed away!'

✅Based on the above narrations and others, denying one of the infallible Imams is like denying all of them and is equivalent to denying the Messenger of Allah (peace be upon him and his family), and denying Imam al-Mahdi (peace be upon him) is like denying all the Imams and the Messenger of Allah (peace be upon them all), and therefore, like Imam Sadiq (peace be upon him), we seek refuge in Allah from denying a proof from His proofs.

اللَّهُمَّ فَصَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ