They brought them clear proofs. and evidences of the truth that they came with.
(But they would not believe what they had already rejected beforehand) meaning the nations did not believe what their Messengers brought to them because they already rejected it from the beginning. Allah said:
(And We shall turn their hearts and their eyes away (from guidance).) (6:110) He then said here,
(Thus We seal the hearts of the transgressors.) This means that as Allah has set seals on the hearts of those people, such that they would not believe since they previously rejected faith, He would also set seals on the hearts of the people that are like them, who will come after them. They would not believe until they see the severe torment. This means that Allah destroyed the nations after Nuh. He destroyed the nations that rejected the Messengers and saved those who believed from among them. From the time of Adam to Nuh, people followed Islam. Then they invented the worship of idols. So Allah sent Nuh to them. That is why the believers will say to him on the Day of Resurrection, "You are the first Messenger Allah sent to the people of the earth." Ibn `Abbas said: "There were ten generations between Adam and Nuh, and all of them were following Islam." Allah also said:
(And how many generations have We destroyed after Nuh!) (17:17) This was a serious warning to the Arab pagans, who rejected the leader and last of the Messengers and Prophets. If the people before them who rejected their Messengers had received this much punishment, then what did they think will happen to them since they perpetrated even greater sins than others before them