Ahmad ibn al-Tayyib al-Sarakhsi was a 9th-century traveller, historian and philosopher. He was a pupil of Al-Kindi

Al-Kindi

' , known as "the Philosopher of the Arabs", was a Muslim Arab philosopher, mathematician, physician, and musician. Al-Kindi was the first of the Muslim peripatetic philosophers, and is unanimously hailed as the "father of Islamic or Arabic philosophy" for his synthesis, adaptation and promotion...

.

Al-Sarakhsi was killed by Caliph Al-Mu'tadid

Al-Mu'tadid

Al-Mu'tadid was the Abbasid Caliph in Baghdad from 892 to 902. As the son and heir of the powerful vizier and virtual regent Al-Muwaffaq , Mu'tadid was already in possession of supreme power even before he was appointed Caliph, and continued as Caliph to ably administer the Government...

 because, according to an anecdote preserved in Yaqut al-Hamawi

Yaqut al-Hamawi

Yāqūt ibn-'Abdullah al-Rūmī al-Hamawī) was an Islamic biographer and geographer renowned for his encyclopedic writings on the Muslim world. "al-Rumi" refers to his Greek descent; "al-Hamawi" means that he is from Hama, Syria, and ibn-Abdullah is a reference to his father's name, Abdullah...

's Mu'jam al-Udaba, he had urged the caliph towards apostasy. Al-Biruni

Al-Biruni

Abū al-Rayḥān Muḥammad ibn Aḥmad al-BīrūnīArabic spelling. . The intermediate form Abū Rayḥān al-Bīrūnī is often used in academic literature...

reports in his Chronology that al-Sarakhsi had written books in which he denounced prophecy and ridiculed the prophets, whome he styled charlatans. However, Rosenthal has disputed the historicity of the stories that claim al-Sarakhsi was executed for heretical beliefs.