Statement by Imam Ibn Hibban:

"He (Imam Tirmidhi) was among the leading Imams of Hadith who collected narrations, authored books on Hadith, memorized Hadith, and engaged in scholarly discussions regarding them." [Al-Thiqat, Tadhkirat al-Huffaz, Nukat al-Himyān by Al-Safadi, Tahdhib al-Kamal]