What is the ruling on the belief that if the plant "Kaff Maryam" (Anastatica hierochuntica) is placed in water and this water is sprinkled in front of people's homes, the girls of that house will get married, and is it permissible to do that?

It is impermissible to adopt as a means what Allah has not made a means, whether by Sacred Law or by Divine Decree. This act is a form of charlatanism and superstition, akin to what the people of the Pre-Islamic Era of Ignorance used to do by taking amulets. It is a minor form of polytheism (shirk asghar) and could lead to major polytheism (shirk akbar).