What's the right of Ahlu ath-Thimmah (non-Muslims living in an Islamic state) regarding their religious practice and their rights in that country?
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu 'alayhi wa sallam, is His slave and Messenger.
With regard to Ahlu ath-Thimmah (free non-Muslim subjects living in a Muslim country), they are the Christians, the Jews, the Magians, and the Sabians who live in the Muslim country.
As a rule, Muslims and Thimmis (Ahlu ath-Thimmah) have the same rights and are subject to the same obligations in the Muslim country. The scholars of Islam confirm such a ruling and build upon it their juristic opinions.
But, there must be some exceptions to the above ruling, since the Muslim country is a state that is based on creed; i.e. it is not possible to put a Muslim and a non-Muslim good and bad on the same level without some limitation.
Allah Says (what means): {Then will We treat the Muslims like the criminals? What is [the matter] with you? How do you judge?} [Quran 68:35-36]
Thus, a Thimmi is not allowed to be the president of the Muslim state or even be a leader in the army or a judge among the Muslims, since such are in fact religious positions to conduct worldly affairs and protect the Muslim authority by applying the religion.
Islam secures personal freedom for the Thimmi in the Muslim state; i.e. no one can bother or jail a Thimmi without a Sharee'ah ruling. Also, they can move about their own property or reside where they like.
So, their houses, properties, shops, and so on, are secured in the Muslim state.
The Prophet and all Caliphs ordered Muslims to treat Ahlu ath-Thimmah kindly and keep their properties safe.
The Prophet said: “Whoever harms a Thimmi, I shall be his opponent on the day of Judgment, and I always defeat the one whom I oppose.” [As-Suyooti in his book al-Jam'i as-Sugheer with a good chain of narrators]
It is essential for a Thimmi to have freedom of belief; i.e. to be free to convert to Islam or remain on their religion, although it is our duty to invite them to Islam and to argue with them kindly.
The above right is one of their fundamental rights and it constitutes the basis of the contract with them. So, the Muslim state has to protect their Churches against internal or external aggression. They also have the right to perform their worship within their temples and villages. But, they are not allowed to show their forms of worship among Muslim gatherings and on roads lest they tempt Muslims.
They have also the right of expression except to invite Muslims to their religion, in word or in deed.
They can benefit from the public facilities of Muslims in all walks of life. The letter of 'Umar Ibn 'Abdul 'Azeez to his governor of al-Basra is one of the glittering characteristics of the Islamic civilization: ‘Look for the Thimmis who become old and weak and who cannot earn their livelihood and devote a grant that may mend their lives.’
The Thimmis are not allowed to sell pork to Muslims or in their Souqs and markets. They are also banned from dealing with Riba (usury and interest).
For more details, you may refer to “Ahkaam ahlu thimma Wal-Musta’mineen”, by 'Abdul Kareem Zaydaan.
Allah knows best.
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