How do we interpret Allah's saying, "Be, and it is," whether the thing already exists or does not yet exist?

Shaykh al-Islam Ibn Taymiyyah clarifies that the verse: {Indeed, Our word to a thing when We intend it is only that We say to it, "Be," and it is} (Qur’an 16:40) pertains to the address of creation (takwīn), not the address of obligation (taklīf). He explains that the non-existent entity in its external reality, to which Allah's knowledge or will for its creation has not been attached, is not addressed. Rather, the entity that is addressed is the known, mentioned, and written thing whose existence has been decreed.