Is it permissible for a husband who suspects his wife's fidelity to spy on her, and what should he do if his suspicions are confirmed?

It is recommended to have a good opinion of one's wife unless there is conclusive proof [to the contrary], while exercising caution, monitoring her, and scheduling her time with acts of obedience. One should not rush into divorce or expose the wife; rather, she should be admonished and punished for what has been proven against her.