Assalam aalekum who is imam ath-Thhabi

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

Imaam Ath-Thahabi was one of the greatest Muslim scholars who lived in the eighth century of Hijrah; he died 748 AH. His name is Muhammad ibn Ahmad ibn ‘Uthmaan ibn Qaymaaz Ath-Thahabi and his nickname is Abu 'Abdallah. He authored many beneficial books, the most famous of which is “Siyar A’laam An-Nubalaa’”.

Early and late Muslim scholars have expressed admiration for his great knowledge and valuable compilations. As-Sabki, a Shaafi'i scholar, wrote about him: "As for our teacher Abu 'Abdallah, he had unrivaled understanding, who was a valuable treasure to whom we referred in case of a extreme difficult knowledge-related matters. He was the best of all times in memorization and his expressions were as pure as gold. He was the senior scholar in the sciences of Jarh and Ta'deel (Criticizing and Praising), and was the best reference in all fields. It is as if the Ummah had gathered in one place, then he looked at them all and would tell the news of those who were present. He taught and trained us in our profession, and led us to be acknowledged among the group (of scholars)." [End of quote]

As-Shawkaani said about At-Thahabi's compilations, "All his compilations are well-received and sought after. People traveled long distances seeking to obtain (and learn) them. They took them (the books he authored) from him (directly from his mouth), passed them to others, read them, copied them during his life and spread them all over the world. His works contain graceful expressions, no one was able to compete with his style from the scholars of his time, before him nor after him. To conclude it, scholars of his time and those who came after him greatly depended on his knowledge, especially in the field of history and biography, and none was able to gather up and write as much as he did in this subject." [End of quote]

Allah Knows best.