What is the ruling on someone who swore by divorcing his wife if she concealed something from him, and then it became clear that she did conceal something?

If a husband conditions the prohibition of his wife on her concealing something, and she conceals it, then the oath is broken. The prohibition of the wife is determined by the husband's intention: if he intended divorce, then it is a divorce; if he intended ẓihār, then it is ẓihār; and if he intended an oath or had no intention, then he is bound by an expiation for an oath (kaffārat yamīn). Since you intended to make her truthful and did not intend divorce or ẓihār, you are bound by an expiation for an oath. Caution must be exercised regarding anger and leniency with these expressions. The wife must commit to truthfulness with her husband.