When does Almighty God say of a thing, "Be, and it is"; is it upon its existence or its non-existence?

The verses (An-Nahl: 40, Yasin: 82) indicate that Allah's power is complete. If He wills a thing, He merely says to it "Be," and it is instantly. The non-existent is called "a thing" because it exists in Allah's knowledge and is written with Him before its creation. The address "Be" is a cosmic, preordained address that indicates the completeness of Allah's power and will, and it is not a prescriptive address directed to an existing being. Rather, it is directed to the non-existent whose existence has been decreed in Allah's knowledge and will. Allah Almighty knows and writes everything before its creation. The thing to which "Be" is said is that which is known and willed, possessing a fixity and distinctness in knowledge and predestination before its actual creation. As for the non-existent, it is not addressed with a prescriptive command because it does not understand or act, nor is it addressed with "Be" as if it were a fixed external entity. Instead, the command of formation and will is directed towards it, and its existence comes into being according to Allah's perfect power.