Usul al-Kafi
Book 4:
The Book of Divine Proof

Chapter 23
Imams are endowed with the divine knowledge

349. 2. Quoting the verse: Nay, here are signs self-evident in the minds of those endowed with knowledge… (Q, 29:49) Imam Jafar as-Sadiq (p) was asked who were the people endowed with knowledge.
In reply, the Imam (p) pointed towards himself (p).