Assalaamu alaykum wa rahmatullaahi wa barakaatuh. Can I enjoin good and forbid evil without determining if the person is Muslim first?

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, sallallahu ‘alayhi wa sallam, is His slave and Messenger.

The non-Muslim should be enjoined to do good and forbidden from doing evil, and the greatest good that he should be enjoined to do is embracing Islam. It is also lawful to forbid evil even if you do not know whether its doer is a Muslim or non-Muslim given the general indication of the hadeeth: "Whoever among you sees an evil and can change it with his hand (by taking action), let him change it with his hand. If he cannot, then with his tongue (by speaking out); and if he cannot, then with his heart (by denouncing it in his heart), and that is the weakest of faith." [Muslim]

Scholars explained which evil should be forbidden from non-Muslims; namely whatever is deemed prohibited in Islam and involves harming Muslims. The Kuwaiti Encyclopedia of Fiqh reads:

"Ihtisaab (enjoining good and forbidding evil) with regards to Thimmis (non-Muslims living in Muslim lands):

40- Thimmis made their covenants with Muslims to be subject to the rulings of Allah and His Messenger, as they chose to live in a land where the rulings of Allah and His Messenger are implemented, contrary to the non-Muslims who signed a Hudnah (truce or peace treaty) with Muslims by virtue of which they continue to live in their lands and are not subject to the rulings of Islam. This is also contrary to the Musta'mans (the non-Muslims who enter a Muslim land and are granted protection by Muslims), who reside in Muslim lands under state protection without settling therein. This is why there is a set or rulings pertaining to Thimmis in particular apart from the other categories of non-Muslims.

An example of these rulings is that if the Thimmis lived with Muslims in the same city or town, they are subject to Hisbah (enjoining good and forbidding evil), just like Muslims. However, they should not be held accountable or punished for the acts which they do not carry out openly if they hold them to be lawful in their religion and the Muslims are not harmed by them, such as Kufr (disbelief), consuming and keeping alcohol, prohibited marriages in Islam (to those who are unlawful to marry because of kinship degree). However if they commit any of this openly, they must be forbidden from doing so. They are also forbidden from doing openly whatever is deemed prohibited by the Islamic laws.

However, if they happened to live in a town without a Muslim population, they are not prevented from doing such acts openly. The same ruling applies to villages, even if some of the population are Muslims, because a village is not a place of proclaiming religion by holding the Friday prayer and 'Eed prayers and where the Hudood (pl. of Hadd; corporal punishment prescribed for certain crimes in the Shariah) and legal verdicts are executed. If they openly commit sinful acts which were not excluded in their covenant with Muslims, such as adultery or lewdness, in their villages, they must be forbidden from it because such evils are not allowed in their religions; rather, it is dissoluteness according to their religions, for they believe that such acts are prohibited, just like the Muslims."

The Hanafi book Al-Mufeed reads, "The Thimmi is forbidden to do whatever the Muslim is forbidden to do except for drinking alcohol and eating pork, because this was excluded in their covenants with Muslims. If they sing and play musical instruments, they are to be forbidden just like the Muslims because this was not excluded in their covenants."

As-Saffaareeni wrote, "If a Thimmi commits evils openly ... the Shariah dictates that he is to be reproached, but if he commits such evils secretly in the privacy of his house, he is not to be reproached." [Manthoomat Al-Aadaab: modified]

Allah knows best.