and Iranians, but sharpened the distinction between Muslims and non-Muslims. The Abbasids zealously persecuted heretics, and although this was directed mainly at Muslim sectarians, it also created a harsher climate for non-Muslims. Survival Despite economic and social incentives to convert, Zoroastrianism remained strong in some regions, particularly in those furthest away from the Caliphate capital at Baghdad. In Bukhara (in present-day Uzbekistan), resistance to Islam required the 9th-century Arab commander Qutaiba to convert his province four times. The first three times the citizens reverted to their old religion. Finally, the governor made their religion "difficult for them in every way", turned the local fire temple into a mosque, and encouraged the local population to attend Friday prayers by paying each attendee two dirhams. The cities where Arab governors resided were particularly vulnerable to such pressures, and in these cases the Zoroastrians were left with no choice but to either conform or migrate to regions that had a more amicable administration. The 9th century came to define the great number of Zoroastrian texts that were composed or re-written during the 8th to 10th centuries (excluding copying and lesser amendments, which continued for some time thereafter). All of these works are in the Middle Persian dialect of that period (free of Arabic words), and written in the difficult Pahlavi script (hence the adoption of the term "Pahlavi" as the name of the variant of the language, and of the genre, of those Zoroastrian books). If read aloud, these books would still have been intelligible to the laity. Many of these texts are responses to the tribulations of the time, and all of them include exhortations to stand fast in their religious beliefs. Some, such as the "Denkard", are doctrinal defenses of the religion, while others are explanations of theological aspects (such as the Bundahishn's) or practical aspects (e.g., explanation of rituals) of it. In Khorasan in northeastern Iran, a 10th-century Iranian nobleman brought together four Zoroastrian priests to transcribe a Sassanid-era Middle Persian work titled Book of the Lord (Khwaday Namag) from Pahlavi script into Arabic script. This transcription, which remained in Middle Persian prose (an Arabic version, by al-Muqaffa, also exists), was completed in 957 and subsequently became the basis for Firdausi's Book of Kings. It became enormously popular among both Zoroastrians and Muslims, and also served to propagate the Sassanid justification for overthrowing the Arsacids (i.e., that the Sassanids had