What is the ruling when one declares an action forbidden by saying 'This is my stepdaughter' with the intent of forbidding her?

Primary text

If one says, 'This is my stepdaughter,' intending to forbid her, this constitutes Zihar (a form of divorce declaration). This is the position of the general body of jurists, without known disagreement, whether the speaker intended an oath or spoke generally. This is because even if one says 'By Allah' and omits 'I swear' or 'I testify' and omits mentioning the action, it is treated as an oath because the preposition 'Ba' (by) relates to an implied future action, and making the implied action explicit confirms the ruling.