Historically, the jizya tax has been understood in Islam as a fee for protection provided by the Muslim ruler to non-Muslims, for the exemption from military service for non-Muslims, for the permission to practice a non-Muslim faith with some communal autonomy in a Muslim state, and as material proof of the non-Muslims' submission to the Muslim state and its laws. Jizya has also been understood by some as a badge or state of humiliation of the non-Muslims in a Muslim state for not converting to Islam, a substantial source of revenue for at least some times and places (such as the Umayyad era), while others argue that if it were meant to be a punishment for the dhimmis' unbelief then monks and the clergy wouldn't have been exempted.