What is the ruling on a husband telling his wife: "If you do this again, it will be the end of us," intending to intimidate her, and is expiation (kaffarah) required of him, and what should he do if he wishes to permit her to do what he had forbidden her from?

The wording issued implies the suspension of the wife's divorce upon her performing a certain action. If the intention was merely a threat and divorce was not intended, then no divorce occurs upon her action, and there is no expiation for it. There is no harm in allowing her to send her pictures in a permissible manner to those for whom it is lawful to look at them, although avoiding that is better due to the possibility of the pictures falling into the hands of those for whom it is not lawful to look at them.