Al-Kāfi - Volume 1 > The Conditions of the Imams in the Matters of Age
Hadith #4

4ـ عَلِيُّ بْنُ مُحَمَّدٍ وَغَيْرُهُ عَنْ سَهْلِ بْنِ زِيَادٍ عَنْ يَعْقُوبَ بْنِ يَزِيدَ عَنْ مُصْعَبٍ عَنْ مَسْعَدَةَ عَنْ أَبِي بَصِيرٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلام) قَالَ أَبُو بَصِيرٍ دَخَلْتُ إِلَيْهِ وَمَعِي غُلامٌ يَقُودُنِي خُمَاسِيٌّ لَمْ يَبْلُغْ فَقَالَ لِي كَيْفَ أَنْتُمْ إِذَا احْتَجَّ عَلَيْكُمْ بِمِثْلِ سِنِّهِ أَوْ قَالَ سَيَلِي عَلَيْكُمْ بِمِثْلِ سِنِّهِ.

4. Ali ibn Muhammad and others have narrated from Sahl ibn Ziyad from Ya‘qub ibn Yazid from Mus‘ab From Mas‘da from abu Basir who has said the following. “Once I went to see him. Along with me there was a of five years old boy who had not yet attained puberty. The Imam (a.s.) said, “How would you feel if people will debate you about the divine authority of someone of his age? Or he said about the Divine authority of one who will come and will be of the same age as his.”