What is the expiation for an oath of "by that which is unlawful and divorce if I bring up the subject, I will discuss it with you," if the intention behind it was not divorce?

If a man makes the prohibition of his wife contingent on a condition, then if this condition occurs, what he intended by the prohibition takes effect. If he intended ẓihār (a pre-Islamic form of divorce), he must offer the expiation for ẓihār. If he intended an oath, or if he did not intend anything specific, then he must offer the expiation for an oath. If he makes divorce contingent on a condition, then it takes effect upon the occurrence of the condition according to the majority of scholars. However, Sheikh al-Islam Ibn Taymiyyah holds that it entails the expiation for an oath. As for cases where the condition upon which the prohibition or divorce was contingent does not occur, no expiation is required. It is advised to avoid uttering phrases of prohibition and divorce as a threat.