Samanid Empire
In the 8th century, a Persian from Balkh known as Saman Khuda left Zoroastrianism for Islam while living under the Umayyads. His children founded the Samanid Empire (875–999). Persian became the official language and had a higher status than Bactrian, because it was the language of Muslim rulers. It eventually replaced the latter as the common language due to the preferential treatment as well as colonization.