Al-Kāfi - Volume 1 > The Imams are those who have received Knowledge and it is firmly Established in their Hearts
Hadith #5

5ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْحُسَيْنِ بْنِ سَعِيدٍ عَنْ مُحَمَّدِ بْنِ الْفُضَيْلِ قَالَ سَأَلْتُهُ عَنْ قَوْلِ الله عَزَّ وَجَلَّ بَلْ هُوَ آياتٌ بَيِّناتٌ فِي صُدُورِ الَّذِينَ أُوتُوا الْعِلْمَ قَالَ هُمُ الائِمَّةُ (عَلَيْهم السَّلام) خَاصَّةً.

5. A number of our people has narrated from Ahmad ibn Muhammad from al-Husayn ibn Sa‘d from Muhammad ibn al-Fudayl who has said that he asked abu ‘Abdallah (a.s.) about the meaning of the following verse of the Holy Quran. “In fact, the Quran consists of illustrious verses that exist in the hearts of those who have knowledge. . .” (29:49) The Imams (a.s.) said, “They are the Imams (a.s.) exclusive of all others.”