Is it permissible to set up a sting operation for a Muslim worker accused of theft in order to prove his crime and hand him over to security?

The basic principle is the impermissibility of having a bad opinion of a just Muslim, unless signs of evil become apparent from him. In such a case, there is no sin in having a bad opinion of him. However, if the person about whom a bad opinion is held is known for being discreet and righteous, and one suspects him of corruption, then that is forbidden. As for one who is known for committing dubious acts and openly engaging in evil deeds, there is no sanctity in him.

There is no objection to setting a trap to identify the thief of the belongings by placing the mobile phone in the restroom, because it is an act of the person concerning his own property. As for searching the worker after he denies taking the mobile phone, there appears to be no impediment to it due to the certainty that he took it, and refraining from searching in this case would lead to the loss of the mobile phone.

Some scholars permit spying and uncovering secrets if it involves a violation of sanctity that would be irrecoverable, such as fear of murder or adultery. In such cases, it is permissible to spy and investigate as a precaution against the loss of something that cannot be recovered. However, if the matter is not so, then spying and uncovering secrets are not permissible.

The hadith of Ali (may Allah be pleased with him) indicates the permissibility of searching when necessary, as he was commanded to search the woman who was carrying a letter from Hatib ibn Abi Balta'ah to the polytheists. It was permissible to search her even though it was not initially proven that she was carrying the letter.

It is not permissible to spy on someone who conceals his immorality, unlike someone who openly declares his immorality; in the latter case, spying on him is not forbidden because he has cast off the garment of modesty. As for someone who conceals sin in his home and locks his door, it is not permissible to spy on him unless something becomes apparent that indicates it, such as hearing the sounds of musical instruments or smelling the odor of wine.