The effect of an oath concerning observing an action, such as seeing one's wife enter a dwelling.
Chapter on Explicit Divorce and Others
Al-Mughni
Book of Divorce
Primary text
If a man swears to his wife, 'You are divorced if I see you enter the dwelling,' the ruling depends entirely on his intention. If he intended that she should never enter, the oath is broken upon her entry. If he intended only that the divorce occurs upon his observation (seeing) of her entry, he is not liable until he witnesses her entering. This is because oaths are fundamentally based on intentions, especially since observation ('seeing') can also signify certain knowledge, as indicated in the Quran, {Have you not seen how your Lord dealt with 'Ad?} [Al-Fajr: 6].
Supporting text
If there is no specific intention or contextual cause indicating the desired result, the oath is not broken unless the literal act mentioned in the oath—her entering the dwelling—occurs, as that is what the wording directly covered.