If I said: “By Allah, I will pay for my brother at the restaurant,” and he paid before me, what is my obligation?

Question:
May Allah reward you, Honorable Shaykh. This questioner says: I always say, “By Allah, I will not do such and such,” and I say, “By Allah, I will pay for my brother at the restaurant,” but he pays before me. What should I do?

Answer:
If you did not intend the oath, and it merely slipped from your tongue without intention, then there is nothing in it; this is a slip of the tongue. However, if you intended to make the oath and you violated it, or the person for whom you swore violated it, then you are required to pay the expiation for it. Yes.