private matters which he cannot disclose to anyone. But if the matter entails no harm to you, then you are instructed to honor his oath. If it benefits your brother, this is even more strongly emphasized; and if it averts harm from him, then it is obligatory.
The point is that the basic ruling on honoring the oath of one who swears is that it is legislated, and that it is among the rights of one Muslim over another. However, circumstances may accompany it that render it prohibited, or that render it obligatory.
But is the expiation due from the one who breaks the oath or from the one who swore it? The answer is: it is due from the one who swore it. Thus, if you frustrate the oath-taker’s oath and do not honor his oath, the expiation is upon him, because he is the one who took the oath, and the expiation pertains to the oath-taker.
So, if the oath-taker says, “You are the one who broke the oath and caused the expiation to become due upon me; therefore, you must offer the expiation, because the one who causes something is like the one who directly does it,” we say: Rather, you are both the direct agent and the cause: you are the one who swore, and you are the one who acted, whereas all I did was bring about the condition for the expiation to become due—namely, the breaking of the oath. As for the original cause, it was you.
Whoever declares lawful things unlawful for himself—other than his wife—whether a slave woman, food, clothing, or anything else, they do not become unlawful; and he must offer the expiation for an oath if he does it.
His statement, “Whoever declares lawful things unlawful for himself—other than his wife—whether a slave woman, food, clothing, or anything else, they do not become unlawful; and he must offer the expiation for an oath if he does it”: “Whoever” is a conditional noun that governs the jussive mood; its conditional verb is “declares unlawful,” and its answer is “they do not become unlawful.” Thus, one who declares unlawful what Allah has made lawful falls into three categories:
First: that he is making an original declaration.
Second: that he is reporting something.