What is the ruling on selling something used for cheating in exams after purchasing it? Is it permissible to sell it to another person or to the source from which it was bought, or is that not permissible and one should seek compensation from Allah, especially since it led to debt?

If the item mentioned is used exclusively for unlawful purposes, then selling it is impermissible, as it constitutes aiding in sin, and this includes deception. Every action that leads to sin, such as selling grapes to someone who will use them to make wine, or selling weapons to disobedient individuals, is forbidden. If the sale is forbidden, then you must speak to the person who sold it to you, inform him of the invalidity of the transaction, return the device to him, ask him to return your money, and warn him against selling items that aid in disobedience. It is obligatory to return an invalidly sold item to its owner if it has not been consumed or destroyed, and it is forbidden for the buyer to benefit from it as long as it exists.