Overall meaning : Have the idolaters among your people, Muhammad, then, not travelled through the land to see and reflect on the fate of the unbelieving nations before them?! The unbelievers in former times were more numerous and greater in strength than the Quraysh unbelievers, and they left considerable marks of their power in the earth; yet neither their great numbers nor their great power proved of any avail to them and did not protect them against Allah’s punishment!
When the messengers of those past unbelieving nations brought them Allah’s clear signs, they conceitedly exulted in whatever worldly knowledge they had, and so they were encompassed by the very punishment they had disbelieved and mocked. And when they saw Our punishment descending upon them, they said, ‘We now believe in Allah alone, and we renounce the false gods we used to worship besides Him!’
But their newly acquired faith was of no benefit to them at all after they had seen Our punishment coming upon them. Allah has established a rule regarding the unbelievers: Beleiving at the time of witnessing His punishment descending upon them will be of no avail to them, nor will their repentance then be accepted. Those who disbelieved in their Lord then perished, suffering a total loss.