Al-Kāfi - Volume 1 > Tacit and Explicit Testimony as proof of abu Muhammad al-Hassan ‘s (a.s.) Divine Authority over the people after Ali ibn Muhammad (a.s.)
Hadith #5

5ـ الْحُسَيْنُ بْنُ مُحَمَّدٍ عَنْ مُعَلَّى بْنِ مُحَمَّدٍ عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ عَبْدِ الله بْنِ مَرْوَانَ الانْبَارِيِّ قَالَ كُنْتُ حَاضِراً عِنْدَ مُضِيِّ أَبِي جَعْفَرٍ مُحَمَّدِ بن علي (عَلَيْهما السَّلام) فَجَاءَ أَبُو الْحَسَنِ (عَلَيْهِ السَّلام) فَوُضِعَ لَهُ كُرْسِيٌّ فَجَلَسَ عَلَيْهِ وَحَوْلَهُ أَهْلُ بَيْتِهِ وَأَبُو مُحَمَّدٍ قَائِمٌ فِي نَاحِيَةٍ فَلَمَّا فَرَغَ مِنْ أَمْرِ أَبِي جَعْفَرٍ الْتَفَتَ إِلَى أَبِي مُحَمَّدٍ (عَلَيْهِ السَّلام) فَقَالَ يَا بُنَيَّ أَحْدِثْ لله تَبَارَكَ وَتَعَالَى شُكْراً فَقَدْ أَحْدَثَ فِيكَ أَمْراً.

5. Al-Husayn ibn Muhammad has narrated from Mu‘alla ibn Muhammad, from Ahmad ibn Muhammad ibn ‘Abdallah ibn Marwan al-Anbari who has said the following. “I was present at the time of abu Ja‘far Muhammad ibn Ali’s (leaving this world). Abu al-Hassan (a.s.) came and a chair was set for him. He sat on it and his family around him. Abu Muhammad was standing on one side. When he was free from the matters about abu Ja‘far he then turned to abu Muhammad (a.s.) and said, “My son, renew thanks to Allah, the Most Holy, the Most High, because He has just granted you a task (Leadership with Divine Authority).”