What is the Shar'i ruling regarding a wife saying to her husband: "You are forbidden to me," or "You are forbidden to me like the sacredness of my father and brother," or "I am forbidden to you"? Does she sin by saying that, and does the marriage contract remain valid? What is its expiation? And what is the ruling if she intended to say that but did not utter it, or if she constantly thought about it without uttering it?

This statement issued by the woman does not affect the infallibility [of the marriage]. As for the aspect of sin:

If she intended it as an oath, she has sinned because she swore by other than Allah.

If she did not intend it as an oath, then she has uttered a statement for which she should be rebuked and admonished, and it is not permissible for her to say to her husband: "You are my brother" or "like my brother."

Contemplating this is not considered a sin, but a Muslim should ponder what benefits them in this world or the hereafter.