Question: what is Khulf al-Wa`d and Khulf al-Wa`id and what is the difference between Imkan al-Kadhib, Khulf al-Wa`d, and Khulf al-Wa`id?
Answer: There is no big difference, just different words for the same thing. Imkan al-Kadhib, means “possibility of saying something untrue,” “Khulf al-Wa`d” means to promise something, and then not do it. “Khulf al-Wa`id,” means to threaten something, and then not do it. When Aļļaah says that the blasphemers will be in Hell forever, for example, then this is a threat that must come true, because Aļļaah does not lie, and nothing can prevent what He wills. When Aļļaah tells us this, it is because He knows what will happen in the future.