Al-Kāfi - Volume 1 > Tacit and Explicit Testimony as proof of abu ‘Abdallah Ja‘far ibn Muhammad al-Sadiq’s (a.s.) Divine Authority over the people after Muhammad ibn Ali ibn al-Husayn (a.s.)
Hadith #2

2ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ هِشَامِ بْنِ سَالِمٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلام) قَالَ لَمَّا حَضَرَتْ أَبِي (عَلَيْهِ السَّلام) الْوَفَاةُ قَالَ يَا جَعْفَرُ أُوصِيكَ بِأَصْحَابِي خَيْراً قُلْتُ جُعِلْتُ فِدَاكَ وَالله لادَعَنَّهُمْ وَالرَّجُلُ مِنْهُمْ يَكُونُ فِي الْمِصْرِ فَلا يَسْأَلُ أَحَداً.

2. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from ibn abu ‘Umayr from Hisham ibn Salim from abu ‘Abdallah (a.s.) who has said the following. “When myfather was about to leave this world he said, “O Ja‘far, I recommend you to be good to my companions.” I then said, “May Allah take my soul in service for your cause, by Allah, I will educated them as such that in any city where any of them would live he would not need to ask others for knowledge (of religion).”