Answer
Under Al-Hajjaj, Muslim religious formulas became strictly enforced on the coinage of the Umayyad caliphate. The religious slogans were previously optional, and a variety of religious, secular, and even pagan inscriptions could be found on the coins. However, under Al-Hajjaj, the coins were inscribed with the words "There is no God but Allah, Muhammad is the messenger of Allah" in a clear and unambiguous fashion.