Tafsir of Al-Waqi'ah 56:57

(We have created you, so why do you not believe?)

This is a shift in address, directed at the disbelievers by way of compulsion and reproach. The fa (so) is for ordering the incitement based on what preceded it; that is: "Why, then, do you not believe in the [act of] creation?" given the evidence provided by "We have created you."

Since their belief—which is implied by His saying, "And if you asked them who created the heavens and the earth, they would surely say, 'Allah'"—was not realized through their actions, as it was not accompanied by obedience and righteous deeds, but rather by what indicates the opposite, such as polytheism and disobedience, it was treated as if it were non-existent or a denial. Thus, they were incited to believe in that [creation].

It has been said that the meaning is: "Why do you not believe in the Resurrection?" due to its prior mention and the fact that their denial of it preceded this in their saying, "Will we really be resurrected?" In this case, the discourse serves as an indication of using the initial creation as proof for the re-creation, for whoever has the power to do the former certainly has the power to do the latter. The first interpretation is the intended face of the argument, as will become apparent from what follows, if Allah the Almighty wills.