Congregational Prayer and Its Virtue
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 57
وَ كَانَ أَمِيرُ اَلْمُؤْمِنِينَ عَلَيْهِ اَلسَّلاَمُ يَقُولُ: «لاَ بَأْسَ أَنْ يُؤَذِّنَ اَلْغُلاَمُ قَبْلَ أَنْ يَحْتَلِمَ وَ لاَ يَؤُمُّ حَتَّى يَحْتَلِمَ فَإِنْ أَمَّ جَازَتْ صَلاَتُهُ وَ فَسَدَتْ صَلاَةُ مَنْ يُصَلِّي خَلْفَهُ.
The Commander of the Faithful Imam Ali ibn Abi Talib عليه السلام said: "There is no problem if a young boy (who has not yet reached puberty) gives the adhan (call to prayer), but he should not lead the prayer until he has reached puberty. If he leads, his own prayer is valid, but the prayer of those who follow him is invalid."
- Ṣaḥīḥ al-Faqīh