Does the husband’s statement to his wife, whose marriage contract has been written but with whom he has not yet consummated the marriage, constitute a Zihar or a divorce: "By Allah, when we get married, your situation will be like the situation of so-and-so (his sister), and everyone will sleep in one place," knowing that his intention was to frighten her and make her feel guilty?

The phrase mentioned could be a threat or a conditional prohibition on her wedding.

If the intention was a threat, then it does not result in ẓihār (declaratory divorce) or divorce, and an expiation for a broken oath (kaffārat yamīn) is due.

If the intention was to condition her prohibition upon her wedding, then this is ẓihār. It is valid when conditional and before consummating the marriage. So, if the wife is wedded, it is not permissible to enjoy her until after performing the expiation for ẓihār mentioned in the Quran.

Some scholars are of the opinion that ẓihār that is made conditional with the intent of threatening has the same ruling as an oath, and the expiation for a broken oath suffices.