After him, after Noah, messengers were sent to their people, meaning Hud, Salih, Ibrahim, Lut, and Shu'ayb. They came to them with clear signs, evidences that confirmed their claims. But they were not to believe; their faith was only impossible, like the impossible, due to their strong stubbornness in disbelief and their determination upon it, because of what they had denied before. This means that they were, before the mission of the messengers, people of ignorance, denying the truth. There was no distinction between their state after the mission of the messengers and before it, as if no one had been sent to them. Thus, we seal such a firm seal upon the hearts of the transgressors. The sealing is a metaphor for their obstinacy and stubbornness, as failure follows it. Do you not see how they were attributed with transgression and described by it?