[They are] those who said, "Indeed, Allāh has taken our promise not to believe any messenger until he brings us an offering which fire [from heaven] will consume." Say, "There have already come to you messengers before me with clear proofs and [even] that of which you speak. So why did you kill them, if you should be truthful?"
They are those who lied in their claim that Allah had instructed them in His scripture and from His prophets to not have faith in a messenger unless he came to them with a charitable offering which fire would then burn from the sky. In their claiming this they also restricted other miraculous signs and evidences the prophets came with. Due to this, Allah instructed His Prophet Muhammad (peace be upon him) to ask them why, when messengers had come to them before with clear proofs of the truth of their message, and even with what they had mentioned of an offering burned by fire from the sky, did they reject them and kill them if they were telling the truth!