What is the Shar'i ruling regarding a husband who does not spend on his wife under the pretext of saving money for the future, and how should the wife act in this situation?

The wife's maintenance is obligatory upon her husband according to what is customary and commensurate with his means. It does not cease due to her wealth unless she absolves him of it. If he does not spend on her, you may take from his money what suffices you, according to what is customary, if you are able. Otherwise, the maintenance remains a debt upon him, and it does not lapse with the passage of time until he pays it or you absolve him of it.