He said, hoping to find a place for denial or confusion: "So bring it," meaning: it resulted from your saying that I say to you: bring that thing, "if you are" [meaning: if you are firmly established in it] "among the truthful" [meaning: in what you claimed of prophethood and evidence]. This indicates that by his previous words, he has become among them in a different category. It is necessary for him that only the truthful can bring the miracle, because it is a confirmation from Allah for the claimant, and His custom, glorified and exalted is He, is that He does not confirm the liar.