Is it permissible to swear by saying: "Haram by Allah"?

Question:
He says: Honorable Shaykh, may Allah grant you success, some people say "Haram by Allah." Does this count as an oath? He says "Haram by Allah," so does this count as an oath? And what is it that is "Haram by Allah"? He says if he wants to swear, he uses this phrase "Haram by Allah." Is this thing haram? What is it that he says is haram? Is it a mubah (permissible) thing that he says is haram?

Answer:
So prohibition is lawful . As for saying "by Allah," this is one of the forms of the oath: the waw, the ba, the taa, "Wallah," "Tallah," "bi-Allah"—these are among the forms of the oath.